THEME 5

physiologicOAnatomICAL peculiarities of the respiratory system. The features of embryogenesis of THE respiratory organs and its maldevelopment. Semiotics of the respiratory system lesions. The syndromes of respiratory distress and failure, general clinical symptoms. Children acute infectious diseases. Medical care and observation Of the child with infectious diseases.

 

Respiratory system in the newborn

 The respiratory tract consists of a complex of structures that function under neural and hormonal control. At birth the respiratory system is relatively small, but after the first breath the lungs grow rapidly. The shape of the chest changes gradually from a relatively round configuration at birth to one that is more or less flattened in the anteroposterior diameter in adulthood (fig. 1). In severe obstructive lung disease the anteroposterior measurement approaches the transverse measurement. Periodic measurements provide clues to the course of lung disease or the efficacy of therapy.

Figure 1.  Anatomical characteristics respiratory tract

 

Changes take place in the air passages that increase respiratory surface area. For example, during the first year the alveoli in the terminal units rapidly increase iumber. In addition, the early globular alveoli develop septa that cause them to become more lobular. They continue to increase steadily until, at the age of 12 years, there are approximately nine times as many as were present at birth. In later stages of growth the structures lengthen and enlarge.

After the early weeks of life the respiratory tract follows the general growth curve. However, the respiratory apparatus grows faster than the vertebral column, resulting in alterations in the relationships between these structures. The bifurcation of the trachea lies opposite the third thoracic vertebra in the infant and gradually descends to a position opposite the fourth vertebra in the adult; the cricoid cartilage descends from the level of the fourth cervical vertebra in the infant to that of the sixth in the adult. These anatomic changes produce differences in the angle of access to the trachea at various ages and must be considered when the infant or child is to be positioned for purposes of resuscitation and airway clearance. The larynx grows slowly until puberty, when its accelerated growth produces changes in the voice that are particularly marked in boys (fig. 2).

Figure 2 Anatomical characteristics lower respiratory tract

 

Respiratory movements are first evident at approximately 20 weeks gestation, and throughout fetal life there is an exchange of amniotic fluid in the alveoli. In the neonate the respiratory rate is rapid to meet the needs of a high metabolism. During growth, the rate steadily decreases in both boys and girls until it levels off at maturity. The volume of air inhaled increases with the growth of the lungs and is closely related to the body size. In addition, there is a qualitative difference in expired air at different ages. The amount of oxygen in the expired air gradually decreases and the amount of carbon dioxide increases during growth. Other important aspects of the respiratory function are discussed as they relate to prenatal life and perinatal adjustments, the newborn infant, and acute and chronic respiratory problems of infants and children (fig. 3).

Figure 3. Physiologicoanatomical peculiarities of the respiratory system

 

 

The main function of the respiratory system is to supply sufficient oxygen to meet metabolic demands and remove carbon dioxide. A variety of processes including ventilation, perfusion, and diffusion are involved in tissue oxygenation and carbon dioxide removal. Abnormalities in any one of these mechanisms can lead to respiratory failure. The pathophysiologic manifestations of respiratory disease processes are profoundly influenced by age- and growth-dependent changes in the physiology and anatomy of the respiratory control mechanisms, airway dynamics, and lung parenchymal characteristics. Smaller airways, a more compliant chest wall, and poor hypoxic drive render a younger infant more vulnerable compared to an older child with similar severity of disease.

 

Peculiarity of the nose in the newborn

 The nose is usually flattened after birth, and bruises are not uncommon. Patency of the nasal canals can be assessed by holding the hand over the infant’s mouth and one canal and noting the passage of air through the unobstructed opening. If nasal patency is questionable, it should be reported because newborns are obligatory nose breathers.

Thin white mucus is very common in the newborn, but a thick, bloody nasal discharge without sneezing may suggest the snuffles of congenital syphilis. Sneezing is very common in the newborn. Flaring of the nares is always noted because it is a serious sign of air hunger from respiratory distress.

 

Peculiarity of the neck in the newborn

         The newborn’s neck is short and covered with folds of tissue. Adequate assessment of the neck requires allowing the head to fall gently backward in hyperextension while the back is supported in a slightly raised position. The doctor observes for range of motion, shape, and any abnormal masses.

 The peculiarities of the nose at the neonate

a) The nose consists particular by of cartilage,

b) The nasal meatuses are narrow,

c) There are not inferior nasal meatuses (until 4 years),

d) Undeveloped submucosal membrane (until 8-9 years).

  

          The peculiarities of sinuses in children

a) The maxillary sinus is usually present at birth,

b) The frontal sinuses begin to develop in early infancy,

c) The ethmoid and sphenoid sinuses develop later in childhood.

 

          The peculiarities of the pharynx at the neonate

a) The pharynx is relatively small and narrow,

b) The auditory tubes are small, wide, straight and horizontal.

 

          The peculiarities of the larynx at the neonate

a) The larynx is funnel-shaped (in the adult it is relatively round),

b) It is relatively long,

c) The cricoid’s cartilage descendents from the level of the fourth cervical vertebra in the infant to that of the sixth in the adult,

d) The fissure of glottis is narrow and its muscles fatigue soon,

e) Vocal ligaments and mucous membrane are very tender, are well blood-supplied,

f)  Vocal ligament are relatively short.

 

          The peculiarities of the trachea at the neonate

a) The length of the trachea is relatively larger (about 4 cm (in the adult -7)) and wide,

b) It is composed of 15-17 cartilage rings (the amount does not increase),

c) The bifurcation of the trachea lies opposite the third thoracic vertebra in infant and descends to a position opposite the fourth vertebra in the adult,

d) Mucus membrane is soft, well-blood supplied, but sometime dry,

f) It can collapse easily.

 

The peculiarities of the bronchi at the neonate

a) In young children the bronchi are relatively wide,

b) The right bronchus is a straight continuation of the trachea,

c) The muscle and elastic fibers are undeveloped,

d) The bronchi are well blood supplied,

e) The lobules and segmental bronchus are narrow.

 

          The functions of the bronchus

a) The ciliated of mucus membrane “sweeps” out dust particles,

b) Transfer the gases into the lungs,

c) Immunologic function.

 

           The functions of the lung are:

a) The main function of the lungs is the exchange of oxygen and carbon dioxide,

b) To produce surfactant

 

           The peculiarities of the lungs at the neonate:

a) Size of alveoli is smaller than in the adult;

b) Quantity of alveoli is relatively less than in the adult.

 

Resistance. The peripheral airway resistance in children younger than 5 years of age is four times higher than adults the major site of resistance is the medium-sized bronchi(fig. 4).

 

 

Figure 4.  Resistance of respiratory tract in children and adults

 

Examination of the chest in children

 Body symmetry is always an important notation during the inspection of the chest. Asymmetry in the chest may indicate serious underlying problems, such as cardiac enlargement (bulging on the left side of the rib cage) or pulmonary dysfunction. However, asymmetry is most often a sign of scoliosis, lateral curvature of the spine. Asymmetry requires further medical investigation.

Movement of the chest wall is noted. It should be symmetric bilaterally and coordinated with breathing. During inspiration the chest rises and expands, the diaphragm descends, and the costal angle increases. During expiration the chest falls and decreases in size, the diaphragm rises, and the costal angle narrows. In children under 6 or 7 years of age, respiratory movement is principally abdominal or diaphragmatic. In older children, particularly females, respirations are chiefly thoracic. In either type the chest and abdomen should rise and fall together.

Any asymmetry of movement is an important pathologyc sign and is reported. Decreased movement on one side of the chest may indicate pneumonia, pneumothorax, atelectasis, or an obstructive foreign body. Marked retraction of muscles either between the ribs (intercostal), above the sternum (suprasternal), or above the clavicles (supraclavicular) is always noted, because it is a sign of respiratory difficulty.

 

Examination of the lungs in children

The lungs are situated inside the thoracic cavity, with one lung on each side of the sternum. Each lung is divided into an apex, which is slightly pointed and rises above the first rib, a base, which is wide and concave and lies on the domeshaped diaphragm, and a body, which is divided into lobes (Fig. 5).

Fig. 5 Lobes and lobules of the lungs

 

The right lung has three lobes: upper, middle, and lower. The left lobe has only two lobes, upper and lower, because of the space occupied by the heart. The two surfaces of the lungs are the costal surface, which faces the chest wall and backs up to the vertebral column, and the mediastinal surface, which faces the space lying between the lungs, the mediastinum. The center of the mediastinal surface is called the hilust where the bronchus and blood vessels enter the lung.

Lung volumes are measured with a spirogram. Tidal volume (V_T) is the amount of air moved in and out of the lungs during each breath; at rest, tidal volume is normally 6-7 mL/kg body weight. Inspiratory capacity (IC) is the amount of air inspired by maximum inspiratory effort after tidal expiration. Expiratory reserve volume (ERV) is the amount of air exhaled by maximum expiratory effort after tidal expiration. The volume of gas remaining in the lungs after maximum expiration is residual volume (RV). Vital capacity (VC) is defined as the amount of air moved in and out of the lungs with maximum inspiration and expiration. VC, IC, and ERV are decreased in lung pathology but are also effort dependent. Total lung capacity (TLC) is the volume of gas occupying the lungs after maximum inhalation (fig. 6, 7).

 

Pulmonary Function Test
1. Anatomical dead space- air in conducting zone where no gas exchange occurs
2. Tidal volume- amount of air expired/breath in quiet breathing
3. Vital capacity- amount of air that can be forcefully exhaled after a maximum inhalation.

 

 

Figure 6. Pulmonary Function – Lung Volumes and capacities

 

Figure 7. The mecanizm of breathing

 

Examination of the lungs requires knowledge of their location and their relationship to the rib cage. The trachea bifurcates slightly below the level of the sternal angle. The lower costal margin crosses the sixth rib at the midclavicular line and the eighth rib at the midaxillary line. The posterior base of the lungs crosses the eleventh rib at the vertebral line. The upper border of the right middle lobe parallels the inferior surface of the fourth rib. Respiration causes displacement of the lobes upward (expiration) or downward (inspiration).

 

Inspection. Inspection of the lungs involves primarily observation of respiratory movements, which are discussed. Respirations are evaluated for (1) rate (number per minute), (2) rhythm (regular, irregular, or periodic), (3) depth (deep or shallow), and (4) quality (effortless, automatic, difficult, or labored). The doctor also notes the character of breath sounds based on inspection without the aid of auscultation, such as noisy, grunting, snoring, or heavy.

 

An average respiratory rate at rest of the child of different age is:

 

 

The respiratory rate is always evaluated in relation to general physical status. For example, tachypnea is expected with fever, because for every degree Fahrenheit elevation in temperature, the respiratory rate increases 4 breaths per minute. The usual ratio of breaths to heartbeats is 1:4.

 

Disorders of the respiratory rate

         Tachypnea is the increase of the respiratory rate.

         Bradypnea is the decrease of the respiratory rate.

         Dyspnea is the distress during breathing.

         Apnea is the cessation of breathing.

 

Disorders of the respiratory depth

         Hyperpnea is an increased depth.

         Hypoventilation is a decreased depth and irregular rhythm.

         Hyperventilation is an increased rate and depth.

 

Pathological respiration

Seesaw (paradoxic) respirations:  the chest falls on inspiration and rises on expiration. It is usually observed in respiratory failure of third degree (Figure 8);

 

Figure 8. Seesaw (paradoxic) respirations

 

 

Kussmaul breathing is a deep and labored breathing pattern often associated with severe metabolic acidosis, particularly diabetic ketoacidosis (DKA) but also renal failure. It is a form of hyperventilation, which is any breathing pattern that reduces carbon dioxide in the blood due to increased rate or depth of respiration.

In metabolic acidosis, breathing is first rapid and shallow but as acidosis worsens, breathing gradually becomes deep, labored and gasping. It is this latter type of breathing pattern that is referred to as Kussmaul breathing.

Kussmaul breathing is respiratory compensation for a metabolic acidosis, most commonly occurring in diabetics in diabetic ketoacidosis. Blood gases on a patient with Kussmaul breathing will show a low partial pressure of CO₂ in conjunction with low bicarbonate because of a forced increased respiration (blowing off the carbon dioxide). Base excess is severely negative. The patient feels an urge to breathe deeply, an “air hunger”, and it appears almost involuntary.

A metabolic acidosis soon produces hyperventilation, but at first it will tend to be rapid and relatively shallow. Kussmaul breathing develops as the acidosis grows more severe. Indeed, Kussmaul originally identified this type of breathing as a sign of coma and imminent death in diabetic patients.

Duration of fasting, presence or absence of hepatomegaly and Kussmaul breathing provide clues to the differential diagnosis of hyperglycemia in the inborn errors of metabolism

 

Cheyne–Stokes respiration is an abnormal pattern of breathing characterized by progressively deeper and sometimes faster breathing, followed by a gradual decrease that results in a temporary stop in breathing called an apnea. The pattern repeats, with each cycle usually taking 30 seconds to 2 minutes. It is an oscillation of ventilation between apnea and hyperpnea with a crescendo-diminuendo pattern, and is associated with changing serum partial pressures of oxygen and carbon dioxide.

Cheyne–Stokes respiration and periodic breathing are the two regions on a spectrum of severity of oscillatory tidal volume. The distinction lies in what is observed at the trough of ventilation: Cheyne–Stokes respiration involves apnea (since apnea is a prominent feature in their original description) while periodic breathing involves hypopnea (abnormally small but not absent breaths).

These phenomena can occur during wakefulness or during sleep, where they are called the central sleep apnea syndrome (CSAS).

It may be caused by damage to respiratory centers, or by physiological abnormalities in chronic heart failure, and is also seen iewborns with immature respiratory systems and in visitors new to high altitudes.

 

Biot’s respiration, sometimes also called ataxic respiration, is an abnormal pattern of breathing characterized by groups of quick, shallow inspirations followed by regular or irregular periods of apnea.

It generally indicates a poor prognosis. Biot’s respiration is caused by damage to the medulla oblongata due to strokes or trauma or by pressure on the medulla due to uncal or tentorial herniation.

It can be caused by opioid use. Related patterns It is distinguished from ataxic respiration by having more regularity and similar-sized inspirations, whereas ataxic respirations are characterized by completely irregular breaths and pauses. As the breathing pattern deteriorates, it merges with ataxic respirations.

In common medical practice, Biot’s respiration is often clinically equivalent to Cheyne-Stokes respiration, although the two definitions are separated in some academic settings.

 

Palpation. Respiratory movements are felt by placing each hand flat against the back or chest with the thumbs in midline along the lower costal margin of the lungs. The child should be sitting during this procedure and, if cooperative, should take several deep breaths. During respiration the hands will move with the chest wall. The doctor evaluates the amount and speed of respiratory excursion, noting any asymmetry of movement. Normally in older children the posterior base of the lungs descends 5 to 6 cm (about 2 inches) during a deep inspiration.

          The doctor also palpates for vocal fremitus, the conduction of voice sounds through the respiratory tract. With the palmar surfaces of each hand on the chest, the doctor asks the child to repeat words, such as “ninety-nine”, “one, two, three,” “eee-eee” or “тридцять три”. The child should speak the words with a voice of uniform intensity. Vibrations are felt as the hands move symmetrically on either side of the sternum and vertebral column. In general vocal fremitus is the most intense in the regions of the thorax where the trachea and bronchi are the closest to the surface, particularly along the sternum between the first and second ribs and posteriorly between the scapulae. Progressing downward, the sound decreases and is least prominent at the base of the lungs.

 

Decreased vocal fremitus in the upper airway may indicate

a) the obstruction of a major bronchus,

b) pneumo-, hydro-, haemothorax,

c) emphysema of lungs,

d) adiposity can also be the cause of decreased vocal fremitus.

 

The voice of fremitus is increased

a) in pneumonia,

b) in abscess,

b) in atelectasis,

c) in cavern.

 

Absence of fremitus usually indicates obstruction of a major bronchus, which may occur as the result of aspiration of a foreign body.

Decreased or absent fremitus is always recorded and reported for further investigation. During palpation other vibrations that indicate pathologic conditions are noted. One is a pleural friction rub, which has a grating sensation. It is synchronous with respiratory movements and is the result of opposing surfaces of the inflamed pleural lining rubbing against one another,

Crepitation is felt as a coarse, cracking sensation as the hand presses over the affected area. It is the result of the escape of air from the lungs into the subcutaneous tissues from an injury or surgical intervention. Both pleural friction rubs and crepitation can usually be heard as well as felt.

 

Percussion. The lungs are percussed in order to evaluate the densities of the underlying organs. Resonance is heard over all the lobes of the lungs that are not adjacent to other organs. Dullness is heard beginning at the fifth interspace in the right midclavicular line. Percussing downward to the end of the liver, a flat sound is heard because the liver no longer overlies the air-filled lung. Cardiac dullness is felt over the left sternal border from the second to the fifth interspace medially to the midclavicular line. Below the fifth interspace on the left side, tympany results from the air-filled stomach. Deviations from these expected sounds are always recorded and reported.

In comparative percussing the chest, the anterior lung is percussed from apex to base, usually with the child in the supine or sitting position (fig. 9). Each side of the chest is percussed in sequence in order to compare the sounds, such as the dullness of the liver on the right side with the tympany of the stomach on the left side. When percussing the posterior lung, the procedure and sequence are the same, although the child should be sitting. Normally only resonance is heard when percussing the posterior thorax from the shoulder to the eighth or tenth rib. At the base of the lungs dullness is heard as the diaphragm is percussed.

 

 

Figure 9. Comparative percussion  

 

The pathological dullness is heard in cause of

a) pneumonia,

b) hydro-, haemothorax,

c) pulmonary edema,

d) lung or mediastinal tumor.

 

The banbox is heard in cause of

a) emphysema of lungs,

b) cavern of lung,

c) abscess of lung,

d) pneumothorax,

e) bronchial asthma,

f) asthmatic bronchitis.

In topographic percussing the chest, the doctor looks for the lungs’ borders in the main lines, the location of the apex of the lung and width of Crenig’s areas. The topographic percussion is used only in children older 7 years old.

 

In topographic percussion the margin of the lung is assessed from the side of resonance sound.

         The location of the lower costal margin of the lungs is shown in Table 1.

Table 1

The lower costal margin of the lungs according the age of the child

 

         

The upper margin of the lung (the location of the apex of the lung) is determined by percussions from the clavicle to the neck. The apex of each lung rises about 2 to 4 cm above the inner third of the clavicles in front of the body At the back we examine the location of the apex of the lung by percussions from the scapula axis to the seventh cervical vertebra. Normally, the upper border of the lung is in the seventh cervical vertebra at the back.

          The width of Crenig’s areas is determined by percussions from the middle of muscle trapezium to each direction (to neck and shoulder) to disappearance of the resonance. Normally, the width of Crenig’s areas is 3-5 cm.

The excursion of the lung is the distance between the lower costal margin of the lungs in the maximum inspiration and maximum expirations. Normally, the excursion of the lung is 2-6 cm.

 

Auscultation. Auscultation involves using the stethoscope to evaluate breath and voice sounds. Breath sounds are best heard if the child inspires deeply. The child can be encouraged to “take a big breath” by following a demonstration of “breathing in through the nose and out through the mouth.” Younger children respond well to games such as blowing out the light from a cigarette lighter or the light of the otoscope.

In the lungs breath sounds are classified as vesicular or bronchovesicular. Vesicular breath sounds are normally heard over the entire surface of the lungs, with the exception of the upper intrascapular area and the area beneath the manubrium. Inspiration is louder, longer, and higher-pitched than expiration. Sometimes the expiratory phase seems nearly absent in comparison to the long inspiratory phase. The sound is a soft, swishing noise. The diagram of vesicular breath sounds may be shown as follows:     

 expiration

inspiration               

 

Bronchovesicular breath sounds are normally heard over the manubrium and in the upper intrascapular regions where there are bifurcations of large airways, such as the trachea and bronchi. Inspiration is louder and higher in pitch than that heard in vesicular breathing.

Puerile breath sounds are one of normal types of breathing in children by three years old. Puerile breath sounds have shot inspiration and louder, a hollow expiratory phase, blowing character.

Another type of breathing that is normal only over the trachea near the suprasternal notch is bronchial breath sounds. They are almost the reverse of vesicular sounds; the inspiratory phase is short and the expiratory phase is longer, louder, and of higher pitch. They are usually louder than any of the normal breath sounds and have a hollow, blowing character. The diagram of bronchial breath sounds is:                 expiration

                     inspiration      

 

Bronchial breathing anywhere in the lungs except over the trachea denotes some abnormality, such as consolidation or compression of the lung tissue (pneumonia, tbc).

Rough breath sounds have shot inspiration and louder expiratory phase. Rough breath has hollow and blowing character. The diagram of rough breath sounds is:

expiration

inspiration   

 

Absent or diminished breath sounds are always an abnormal finding warranting investigation. Fluid, air, or solid masses in the pleural space all interfere with the conduction of breath sounds (pneumonia, pneumo-, hydro-, haemothorax, tumor of lung or mediastinal, emphysema of lungs, atelectasis, airways obstruction, a foreing body in the bronchus). Diminished breath sounds in certain segments of the lung can alert the doctor to pulmonary areas that may benefit from postural drainage and percussion. Increased breath sounds following pulmonary therapy indicate improved passage of air through the respiratory tract.

Voice sounds are also part of auscultation of the lungs. Normally voice sounds or vocal resonance is heard, but the syllables are indistinct. They are elicited in the same manner as vocal fremitus, except that the doctor listens with the stethoscope. Consolidation of the lung tissue produces three types of abnormal voice sounds.

1. Whispered pectoriloquy, in which the child whispers words and the nurse, hears the syllables.

2.  Bronchophony, in which the child speaks words that are not distinguishable but the vocal resonance is increased in intensity and clarity.

3.  Egophony, in which the child says “ee,” which is heard as the nasal sound “ay” through the stethoscope.

Decreased or absent vocal resonance is caused by the same conditions that affect vocal fremitus.

 

 

Auscultation is perhaps the most important and effective clinical technique you will ever learn for evaluating a patient’s respiratory function. Before you begin, there are certain things that you should keep in mind:

          a) It is important that you try to create a quiet environment as much as possible. This may be difficult in a busy emergency room or in a room with other patients and their visitors.

 

Eliminate noise by closing the door and turning off any radios or televisions in the room.

          b) The patient should be in the proper position for auscultation, i.e. sitting up in bed or on the examining table, ensuring that his or her chest is not leaning against anything. If this is not possible, ask for assistance or perform only a partial assessment of the patient’s breathing.

          c) Your stethoscope should be touching the patient’s bare skin whenever possible or you may hear rubbing of the patient’s clothes against the stethoscope and misinterpret them as abnormal sounds. You may wish to wet the patient’s chest hair with a little warm water to decrease the sounds caused by friction of hair against the stethoscope.

          d) Always ensure patient comfort. Be considerate and warm the diaphragm of your stethoscope with your hand before auscultation.

 

As you are auscultating your patient, please keep in mind these 2 questions:

1) Are the breath sounds increased, normal, or decreased?

2) Are there any abnormal or adventitious breath sounds?

 

To assess the posterior chest, ask the patient to keep both arms crossed in front of his/her chest, if possible.

Auscultate using the diaphragm of your stethoscope. Ask the patient not to speak and to breathe deeply through the mouth. Be careful that the patient does not hyperventilate. You should listen to at least one full breath in each location. It is important that you always compare what you hear with the opposite side. e.g. If you are listening to the left apex, you should follow through by comparing what you heard with what you hear at the right apex.

There are between 12 and 14 locations for auscultation on the anterior and posterior chest respectively. Generally, you should listen to at least 6 locations on both the anterior and posterior chest. Begin by ausculating the apices of the lungs, moving from side to side and comparing as you approach the bases. Making the order of the numbers in the images below a ritual part of your pulmonary exam is a way of ensuring that you compare both sides every time and you’ll begin to know what each area should sound like under normal circumstances.

If you hear a suspicious breath sound, listen to a few other nearby locations and try to delineate its extent and character.

There are between 12 and 14 locations for auscultation on the anterior and posterior chest respectively. Generally, you should listen to at least 6 locations on both the anterior and posterior chest. Begin by ausculating the apices of the lungs, moving from side to side and comparing as you approach the bases. Making the order of the numbers in the images below a ritual part of your pulmonary exam is a way of ensuring that you compare both sides every time and you’ll begin to know what each area should sound like under normal circumstances.

          If you hear a suspicious breath sound, listen to a few other nearby locations and try to delineate its extent and character.

 

Breath Sounds

          Breath sounds can be divided and subdivided into the following categories:

          Normal

          Abnormal

          Adventitious

          tracheal

          absent/decreased

          crackles (rales)

          vesicular

          bronchial

          wheeze

          bronchial

          rhonchi

          bronchovesicular

          stridor

          pleural rub

          mediastinal crunch (Hamman’s sign)

 

Normal Breath Sounds

          These are traditionally organized into categories based on their intensity, pitch, location, and inspiratory to expiratory ratio. Breath sounds are created by turbulent air flow. In inspiration, air moves into progressively smaller airways with the alveoli as its final location. As air hits the walls of these airways, turbulence is created and produces sound. In expiration, air is moving in the opposite direction towards progressively larger airways. Less turbulence is created, thus normal expiratory breath sounds are quieter than inspiratory breath sounds.

          tracheal breath sound. Tracheal breath sounds are very loud and relatively high-pitched. The inspiratory and expiratory sounds are more or less equal in length. They can be heard over the trachea, which is not routinely auscultated.

          vesicular breath sound.  The vesicular breath sound is the major normal breath sound and is heard over most of the lungs. They sound soft and low-pitched. The inspiratory sounds are longer than the expiratory sounds. Vesicular breath sounds may be harsher and slightly longer if there is rapid deep ventilation (eg post-exercise) or in children who have thinner chest walls. As well, vesicular breath sounds may be softer if the patient is frail, elderly, obese, or very muscular.

          bronchial breath sound. Bronchial breath sounds are very loud, high-pitched and sound close to the stethoscope. There is a gap between the inspiratory and expiratory phases of respiration, and the expiratory sounds are longer than the inspiratory sounds. If these sounds are heard anywhere other than over the manubrium, it is usually an indication that an area of consolidation exists (ie space that usually contains air now contains fluid or solid lung tissue).

          bronchovesicular breath sound. These are breath sounds of intermediate intensity and pitch. The inspiratory and expiratory sounds are equal in length. They are best heard in the 1st and 2nd ICS (anterior chest) and between the scapulae (posterior chest) – ie over the mainstem bronchi. As with bronchial sounds, when these are heard anywhere other than over the mainstem bronchi, they usually indicate an area of consolidation.

 

Abnormal Breath Sounds

Absent or Decreased Breath Sounds. There are a number of common causes for abnormal breath sounds, including:

          • ARDS: decreased breath sounds in late stages

          • Asthma: decreased breath sounds

          • Atelectasis: If the bronchial obstruction persists, breath sounds are absent unless the atelectasis occurs in the RUL in which case adjacent tracheal sounds may be audible.

          • Emphysema: decreased breath sounds

          • Pleural Effusion: decreased or absent breath sounds. If the effusion is large, bronchial sounds may be heard.

          • Pneumothorax: decreased or absent breath sounds

Bronchial Breath Sounds in Abnormal Locations Bronchial breath sounds occur over consolidated areas.

 

Adventitious Breath Sounds

          Crackles (Rales) Crackles are discontinuous, non-musical, brief sounds heard more commonly on inspiration.

They can be classified as fine (high pitched, soft, very brief) or coarse (low pitched, louder, less brief). When listening to crackles, pay special attention to their loudness, pitch, duration, number, timing in the respiratory cycle, location, pattern from breath to breath, change after a cough or shift in position. Crackles may sometimes be normally heard at the anterior lung bases after a maximal expiration or after prolonged recumbency.

The mechanical basis of crackles: Small airways open during inspiration and collapse during expiration causing the crackling sounds. Another explanation for crackles is that air bubbles through secretions or incompletely closed airways during expiration.

Conditions:

          • ARDS

          • asthma

          • bronchiectasis

          • chronic bronchitis

          • consolidation

          • early CHF

          • interstitial lung disease

          • pulmonary oedema

 

 Adventitious Breath Sounds

Crackles (Rales). Crackles are discontinuous, non-musical, brief sounds heard more commonly on inspiration.

          They can be classified as fine (high pitched, soft, very brief) or coarse (low pitched, louder, less brief). When listening to crackles, pay special attention to their loudness, pitch, duration, number, timing in the respiratory cycle, location, pattern from breath to breath, change after a cough or shift in position. Crackles may sometimes be normally heard at the anterior lung bases after a maximal expiration or after prolonged recumbency.

          The mechanical basis of crackles: Small airways open during inspiration and collapse during expiration causing the crackling sounds. Another explanation for crackles is that air bubbles through secretions or incompletely closed airways during expiration.

          Conditions:

          • ARDS

          • asthma

          • bronchiectasis

          • chronic bronchitis

          • consolidation

          • early CHF

          • interstitial lung disease

          • pulmonary oedema

 

Wheeze

          Wheezes are continuous, high pitched, hissing sounds heard normally on expiration but also sometimes on inspiration. They are produced when air flows through airways narrowed by secretions, foreign bodies, or obstructive lesions.

          Note when the wheezes occur and if there is a change after a deep breath or cough. Also note if the wheezes are monophonic (suggesting obstruction of one airway) or polyphonic (suggesting generalized obstruction of airways).

          Conditions:

          • asthma

          • CHF

          • chronic bronchitis

          • COPD

          • pulmonary oedema

 

Rhonchi

          Rhonchi are low pitched, continuous, musical sounds that are similar to wheezes. They usually imply obstruction of a larger airway by secretions.

 

Stridor

          Stridor is an inspiratory musical wheeze heard loudest over the trachea during inspiration.

          Stridor suggests an obstructed trachea or larynx and therefore constitutes a medical emergency that requires immediate attention.

 

Pleural Rub

          Pleural rubs are creaking or brushing sounds produced when the pleural surfaces are inflamed or roughened and rub against each other. They may be discontinuous or continuous sounds.

          They can usually be localized a particular place on the chest wall and are heard during both the inspiratory and expiratory phases.

          Conditions:

          pleural effusion

          pneumothorax

 

Mediastinal Crunch (Hamman’s sign)

          Mediastinal crunches are crackles that are synchronized with the heart beat and not respiration. They are heard best with the patient in the left lateral decubitus postion. As with stridor, mediastinal crunches should be treated as medical emergencies.

          Conditions:

          pneumomediastinum

          Summary

 

Wheeze

          Wheezes are continuous, high pitched, hissing sounds heard normally on expiration but also sometimes on inspiration. They are produced when air flows through airways narrowed by secretions, foreign bodies, or obstructive lesions.

          Note when the wheezes occur and if there is a change after a deep breath or cough. Also note if the wheezes are monophonic (suggesting obstruction of one airway) or polyphonic (suggesting generalized obstruction of airways).

          Conditions:

          • asthma

          • CHF

          • chronic bronchitis

          • COPD

          • pulmonary oedema

 

 

Rhonchi

          Rhonchi are low pitched, continuous, musical sounds that are similar to wheezes. They usually imply obstruction of a larger airway by secretions.

 

Stridor

          Stridor is an inspiratory musical wheeze heard loudest over the trachea during inspiration.

          Stridor suggests an obstructed trachea or larynx and therefore constitutes a medical emergency that requires immediate attention.

 

Pleural Rub

          Pleural rubs are creaking or brushing sounds produced when the pleural surfaces are inflamed or roughened and rub against each other. They may be discontinuous or continuous sounds.

          They can usually be localized a particular place on the chest wall and are heard during both the inspiratory and expiratory phases.

          Conditions:

          pleural effusion

          pneumothorax

 

Mediastinal Crunch (Hamman’s sign)

          Mediastinal crunches are crackles that are synchronized with the heart beat and not respiration. They are heard best with the patient in the left lateral decubitus postion. As with stridor, mediastinal crunches should be treated as medical emergencies.

Conditions:

          pneumomediastinum

 

 

 

Examination of the Respiratory System  (video).

 

 

Interpretation of Clinical Signs to Localize the Site of Pathology

The 1st step in establishing the diagnosis of respiratory disease is appropriate interpretation of clinical findings. Respiratory distress can occur without respiratory disease, and severe respiratory failure can be present without significant respiratory distress. Diseases characterized by CNS excitation, such as encephalitis, and neureoexcitatory drugs are associated with central neurogenic hyperventilation. Similarly, diseases that produce metabolic acidosis, such as diabetic ketoacidosis, salicylism, and shock, result in hyperventilation as a compensatory response. Patients in either group could be considered clinically to have respiratory distress; they are distinguished from patients with respiratory disease by their increased tidal volume as well as the respiratory rate. Their blood gas values reflect a low Paco₂ and a normal Pao₂. Patients with neuromuscular diseases, such as Guillain-Barre syndrome or myasthenia gravis, and those with an abnormal respiratory drive can develop severe respiratory failure but are not able to mount sufficient effort to appear in respiratory distress. In these patients, respirations are ineffective or can even appear normal in the presence of respiratory acidosis and hypoxemia.

The rate and depth of respiration and the presence of retractions, stridor, wheezing, and grunting are valuable signs in localizing the site of respiratory pathology (table 6). Rapid and shallow respirations (tachypnea) are characteristic of parenchymal pathology, in which the elastic work of breathing is increased disproportionately to the resistive work of breathing. Chest wall, intercostal, and suprasternal retractions are most striking, with increased negative intrathoracic pressure during inspiration. This occurs in extrathoracic airway obstruction as well as diseases of decreased compliance. Inspiratory stridor is a hallmark of extrathoracic airway obstruction. Expiratory wheezing is characteristic of intrathoracic airway obstruction, either extrapulmonary or intrapulmonary. Grunting is produced by expiration against a partially closed glottis and is an attempt to maintain positive airway pressure during expiration for as long as possible. Such prolongation of positive pressure is most beneficial in alveolar diseases that produce widespread loss of FRC, such as in pulmonary edema, hyaline membrane disease, and pneumonia. Grunting is also effective in small airway obstruction (bronchiolitis) to maintain a higher positive pressure in the airway during expiration, decreasing the airway collapse.

 

Interpreting the clinical signs of respiratory disease

 

 

 

Acute viral infections of respiratory tracts

Acute viral infections of respiratory tracts (AVIR) are a group of diseases of the upper and medium respiratory tracts, mostly of virus (H. Influenzae, parainfluenzae, adeno- and rhino-viruses, virus-ECHO, etc), sometimes of microbial (B-hemolytic streptococcus of group A, pneumococcus) etiology. I ocal manifestations of AVIR are: rhinitis, pharyngitis, laryngitis; in most cases bronchitis in children is also considered as AVIR.

 

Acute rhinitis is the inflammation of mucous membrane of the nose, mostly of viral etiology.

Clinical manifestations:

•  Sneezing.

•  Complicated nasal respiration.

•  The excretion of mucus from the nose (at the beginning serous, watery, then more thick).

• Cough (it is caused by the irritation of the back wall of pharynx by mucus refluxing from the nose).

• The general manifestations — weakness, headache, fever; at breast-feeding age — complicated process of sucking.

 

The acute pharyngitis is an inflammation of the mucous membrane of oropharynx — can be both of viral and bacterial etiology. In the latter case, it is often caused by p-hemolytic streptococcus of group A, which can be a factor of rheumatic fever, glomerulonephritis.

Clinical manifestations:

• Hyperemia of the pharynx.

• Increased follicle on the back wall of oropharynx— a symptom of ‘cobblestone road’.

• Pain at swallowing.

• Coughing.

• General manifestations of intoxication.

In children of early age AVIR can be complicated with otitis (explain the anatomic reason).

 

Acute laryngitis, is an inflammation of the mucous membrane of the larynx of viral or bacterial etiology. Children under 3 years of age with laryngitis have stenosis (i.e. narrowing) of the opening of larynx, which is caused by the anatomic features at this age recollect. The developing syndrome refers to ‘false croup ( pseudo-croup)’ and the diagnosis is constrictive laryngotracheitis.

Clinical manifestations:

•        ‘Barking’ cough.

•        A hoarse voice, in severe cases — aphonia.

•        Inspiratory dyspnea (explain the reason and its sign).

•        Tachycardia.

•        Weakness, lethargy, acute laryngitis which is often interchangeable with restlessness.

•        The general manifestations, characteristic for intoxication.

The development of false croup is dangerous for life of the child as in the? neglected cases, the progressing stenosis can lead to asphyxia — the pathological condition menacing the life in theform of suffocation. Simultaneously, tachycardia is replaced by bradycardia, and then heart failure follows. The only way of treatment is intubation or tracheostomy.

 

Croup is a common, primarily pediatric viral respiratory tract illness. As its alternative names, laryngotracheitis and laryngotracheobronchitis, indicate, croup generally affects the larynx and trachea, although this illness may also extend to the bronchi. It is the most common etiology for hoarseness, cough, and onset of acute stridor in febrile children. Symptoms of coryza may be absent, mild, or marked. The vast majority of children with croup recover without consequences or sequelae; however, it can be life-threatening.

Croup manifests as hoarseness, a seal-like barking cough, and a variable degree of respiratory distress. However, morbidity is secondary to narrowing of the larynx and trachea below the level of the glottis (subglottic region), causing the characteristicaudible inspiratory stridor.

Stridoris a common symptom in patients with croup. The acute onset of this abnormal sound alarms parents enough to prompt an urgent care or emergency department (ED) visit. Stridor is an audible harsh, high-pitched, musical sound produced by turbulent airflow through a partially obstructed upper airway. This partial airway obstruction can be present at the level of the supraglottis, glottis, subglottis, and/or trachea. During inspiration, areas of the airway that are easily collapsible (eg, supraglottic region) are suctioned closed because of negative intraluminal pressure generated during inspiration. These same areas are forced open during expiration.

Depending on timing within the respiratory cycle, stridor can be heard on inspiration, expiration, or in both (biphasic; inspiratory and expiratory). Inspiratory stridor suggests a laryngeal obstruction, whereas expiratory stridor suggests tracheobronchial obstruction. Biphasic stridor indicates either a subglottic or glottic anomaly. An acute onset of marked inspiratory stridor is one of the hallmarks of croup; however, there also may be less audible expiratory stridor.

Young children who present with stridor require a meticulous evaluation to determine the etiology and, most importantly, to exclude rare life-threatening causes. Although croup is usually a mild, self-limited disease, upper airway obstruction may result in respiratory distress and even death.

Physical Examination. The physical presentation of croup has wide variation. Most children have no more than a “croupy” cough and hoarse cry. Some may have stridor only upon activity or agitation, whereas others have audible stridor at rest and clinical evidence of respiratory distress. Paradoxically, a severely affected child may have “quiet” stridor secondary to a greater degree of airway obstruction. The child with croup typically does not appear toxic.

The child’s symptoms can range from minimal inspiratory stridor to severe respiratory failure secondary to airway obstruction.In mild cases, respiratory sounds at rest are normal; however, mild expiratory wheezing may be heard. Children with more severe cases have inspiratory and expiratory stridor at rest with visible suprasternal, intercostal, and subcostal retractions. Air entry may be poor. Lethargy and agitation may be due to marked respiratory difficulty and, hence, hypoxemia and increasing hypercarbia.

Other warning signs of severe respiratory disease include tachypnea, tachycardia out of proportion to fever, and hypotonia. Children unable to maintain adequate oral intake, results in compromised hydration and can lead to dehydration. Cyanosis is a late, ominous sign.

Croup is primarily a clinical diagnosis, with the diagnostic clues based on presenting history and physical examination findings.

Laboratory test results rarely contribute to confirming this diagnosis. The complete blood cell (CBC) count is usually nonspecific, although the white blood cell (WBC) count and differential may suggest a viral cause with lymphocytosis. Identifying the specific viral etiology (eg, parainfluenza virus serotype, respiratory syncytial virus [RSV]) via nasal washings is typically not necessary but may be useful to determine isolatioeeds in the hospital care setting or, in the case of influenza A, to decide whether antiviral therapy should be initiated.

Pulse oximetry readings are within the normal reference range for most patients; however, this monitoring is helpful to assess for the need for supplemental oxygen support and to monitor for worsening respiratory compromise as evidentwith tachypnea and poor maintenance of oxygen saturations. Standardly, arterial blood gas (ABG) measurements are unnecessary and do not reveal hypoxia or hypercarbia unless respiratory fatigue ensues.

Patients who present with fevers, tachypnea, and history of decreased oral fluid intake require evaluation of their hydration status. Compromised oral intake and inability to maintaieeded fluid volume may require intravenous fluid support to stabilize, support and sustain their ongoing fluid requirements.

Procedures

Laryngoscopy is indicated only in unusual circumstances (eg, the course of illness is not typical, the child has symptoms that suggest an underlying anatomic or congenital disorder). This procedure may also be required in patients with bacterial tracheitis to obtain the necessary cultures in an attempt to tailor antibiotic treatment.

Other procedures that may be indicated and may require the guidance of a pediatric otolaryngologist include the following:

• Direct laryngoscopy if the child iot in acute distress

• Fiberoptic laryngoscopy

• Bronchoscopy (for cases of recurrent croup to rule out airway disorders)

Radiography. Plain films can verify a presumptive diagnosis or exclude other disorders causing stridor and hence mimic croup. A lateral neck radiograph can help detect clinical diagnoses such as an aspirated foreign body, esophageal foreign body, congenital subglottic stenosis, epiglottitis, retropharyngeal abscess or bacterial tracheitis (thickened trachea).Most importantly, croup is a clinical diagnosis. Radiographs can be used as a tool to help confirm this diagnosis, but they are not required in uncomplicated cases.

Concurrently, careful monitoring of the heart rate (for tachycardia), respiratory rate (for tachypnea), respiratory mechanics (for sternal wall retractions), and pulse oximetry (for hypoxia) are important. Assessment of the patient’s hydration status, given the risk of increased insensible losses from fever and tachypnea, along with a history of decreased oral intake, is also imperative.

Treatment. Urgent care or emergency department treatment of croup depends on the degree of respiratory distress. In mild croup, a child may present with only a croupy cough and may require nothing more than parental reassurance, given alertness, baseline minimal respiratory distress, proper oxygenation, and stable fluid status. The caregivers may only need education regarding the course of the disease and supportive homecare guidelines.

However, any infant/child who presents with significant respiratory distress/complaints with stridor at rest must have a thorough clinical evaluation to ensure the patency of the airway and maintenance of effective oxygenation and ventilation. Keep young children as comfortable as possible, allowing him or her to remain in a parent’s arms and avoiding unnecessary painful interventions that may cause agitation, respiratory distress, and lead to increased oxygen requirements. Persistent crying increases oxygen demands, and respiratory muscle fatigue can worsen the obstruction.

Concurrently, careful monitoring of the heart rate (for tachycardia), respiratory rate (for tachypnea), respiratory mechanics (for sternal wall retractions), and pulse oximetry (for hypoxia) are important. Assessment of the patient’s hydration status, given the risk of increased insensible losses from fever and tachypnea, along with a history of decreased oral intake, is also imperative.

Infants and children with severe respiratory distress or compromise may require 100% oxygenation with ventilation support, initially with a bag-valve-mask device. If the airway and breathing require further stabilization due to increasing respiratory fatigue and hence, worsening hypercarbia, (as evident by ABG) the patient should be intubated with an endotracheal tube. Intubation should be accomplished with an endotracheal tube that is 0.5-1 mm smaller than predicted. Once airway stabilization is achieved, these patients are transferred for their ongoing care to a pediatric intensive care unit.

The current cornerstones of treatment in the urgent care clinics or emergency departments are corticosteroids and nebulized epinephrine; steroids have proven beneficial in severe, moderate, and even mild croup. In the straightforward cases of croup, antibiotics are not prescribed, as the primary cause is viral. Lack of improvement or worsening of symptoms can be due to a secondary bacterial process, which would require the use of antimicrobials for treatment. Typically, these patients initially would have had moderate-to-severe croup scores, requiring inpatient care and observation.

 

Epiglottitis, also termed supraglottitis or epiglottiditis, is an inflammation of structures above the insertion of the glottis and is most often caused by bacterial infection. Before widespread Haemophilus influenzae type b (Hib) vaccination, H influenzae caused almost all pediatric cases of epiglottitis.

Affected structures include the epiglottis, aryepiglottic folds, arytenoid soft tissue, and, occasionally, the uvula. The epiglottis is the most common site of swelling. Acute epiglottitis and associated upper airway obstruction has significant morbidity and mortality and may cause respiratory arrest and death.

The following image illustrates the difference between a normal pediatric airway and one from a child with fatal epiglottitis.

Complications

During the bacteremic phase of the disease, other foci of infection are possible. Pneumonia is the most commonly cited associated illness, followed by otitis media. Meningitis has also been reported in association with epiglottitis.

As with other causes of upper airway obstruction, pulmonary edema can be observed after the airway has been secured. Accidental extubation and respiratory arrest are the 2 most common complications, and accidental extubation can cause additional complications. Cervical adenitis, tonsillitis, and otitis media have also been documented.

In summary, complications associated with a swollen epiglottis and surrounding tissues include airway obstruction, which can lead to respiratory arrest and death from hypoxia as well the following:

·        Aspiration

·        Endotracheal tube dislodgement

·        Extubation

·        Tracheal stenosis

·        Pneumothorax or pneumomediastinum

·        Epiglottic abscess

·        Adenitis

·        Cervical cellulitis

·        Septic shock

·        Pulmonary edema (rare)

·        Cerebral anoxia

·        Death from asphyxia

In classic cases involving bacteremia with Haemophilus influenzae, other structures may have concomitant infectious processes. These may include the following:

·        Meningitis

·        Pneumonia

·        Septicemia

·        Cellulitis

·        Septic arthritis

·        Otitis media

·        Pericarditis (rare)

Physical Examination. The child appears toxic; shock may occur early in the course of the disease. Marked restlessness, irritability, and extreme anxiety are common. The child may sit with his or her chin hyperextended and body leaning forward (ie, tripod or sniffing position) to maximize air entry and improve diaphragmatic excursion (see the following image).The mouth may be open wide and the tongue may protrude; an affected child often drools, because swallowing is difficult or painful. An erythematous and classic swollen, cherry red epiglottis can often be seen during careful examination of the oropharynx, although this examination should not be attempted if it may compromise respiratory effort. Early on, the child may have stridulous respirations, but as the disease progresses, airway sounds may diminish. Stridor can occur with marked suprasternal, subcostal, and intercostal retractions. Anterior neck examination may reveal tender adenopathy. In the older child, pain may be noted on movement of the hyoid bone. Cyanosis, which occurs late in the course of the condition, indicates a poor prognosis. Securing an airway is the overriding priority. An expert in pediatric airway management should always perform an endotracheal intubation on any child with suspected epiglottitis before radiography or blood work is performed. 

Workup. Laryngoscopy is the best way to confirm the diagnosis, but it is not advised to attempt any procedures without securing the airway. Simply depressing the child’s tongue with a tongue blade may visualize the epiglottitis in some situations. Some concern exists regarding the safety of such procedures, which can provoke anxiety and increased respiratory effort during examination leading to airway obstruction.

Laboratory evaluation is nonspecific in patients with epiglottitis and should be performed once the airway is secured. The white blood cell (WBC) count may be elevated from 15,000-45,000 cells/µL with a predominance of bands. Histologic examination reveals massive infiltration with polymorphonuclear leukocytes and inflammatory edema.

Classic cases of epiglottitis require no radiographic evaluation; however, radiography may be needed in some cases to confirm the diagnosis and to exclude other potential causes of acute airway obstruction. When radiography is required to exclude other diagnoses, perform portable radiography at the patient’s bedside.

Recommendations for computed tomography (CT) scanning of the neck in early or unusual cases have been suggested,although great care should be used because of the positioning of the patient.

If epiglottitis is in the differential diagnosis, the child should never be left alone even if imaging studies are being obtained. The child should always be accompanied by personnel who are able to achieve rapid airway access if needed.

Fiberoptic Laryngoscopy

Laryngoscopy can help exclude other diagnoses in an older child who is cooperative. However, do not perform a laryngoscopy if the procedure might increase anxiety, which can exacerbate the airway obstruction.

The naris can be anesthetized with lidocaine jelly before inserting the fiberoptic laryngoscope. Insert the laryngoscope through the naris, advancing it slowly into the supraglottic region. The epiglottis should be easily visualized to determine the presence of swelling.

A study performed in Germany recommended laryngoscopy to aid in the diagnosis in patients with atypical presentations or with crouplike coughs. This study also showed that fiberoptic endoscopy is especially useful in cooperative older children with moderate respiratory distress.

Percutaneous Transtracheal Ventilation

Also termed needle cricothyrotomy or translaryngeal ventilation, percutaneous transtracheal ventilation is a temporizing method used to treat cases of severe epiglottitis when the patient cannot be intubated before a formal tracheostomy.

Percutaneous transtracheal ventilation involves inserting a needle through the cricothyroid membrane, which lies inferior to the thyroid cartilage and superior to the cricoid cartilage. The cricothyroid arteries typically course through the superior portion of the membrane.

Treatment in patients with epiglottitis is directed toward relieving the airway obstruction and eradicating the infectious agent. Optimally, initial treatment is provided by a pediatric anesthesiologist and either a pediatric surgeon or a pediatric otolaryngologist. Once the airway is controlled, a pediatric intensivist is required for inpatient management.

Avoid procedures that might increase the child’s anxiety until after the child’s airway is secured. Procedures such as venipuncture and intravenous access, although appropriate in most cases involving children with acute epiglottitis, may heighten anxiety and precipitate airway compromise.

Do not underestimate the potential for sudden deterioration. As soon as epiglottitis is suspected, initiating and mobilizing a medical and surgical team capable of securing the airway is imperative.

Never place a child in a supine position (other than during the endotracheal intubation procedure), because immediate respiratory arrest in this position has been reported.

 

Acute bronchitis is a clinical syndrome produced by inflammation of the trachea, bronchi, and bronchioles. In children, acute bronchitis usually occurs in association with viral respiratory tract infection. Acute bronchitis is rarely a primary bacterial infection in otherwise healthy children.

Examples of normal airway color and architecture and an airway in a patient with chronic bronchitis are shown below.

Normal airway color and architecture (in a child with mild tracheomalacia). Airway of a child with chronic bronchitis shows erythema, loss of normal architecture, and swelling.

Symptoms of acute bronchitis usually include productive cough and sometimes retrosternal pain during deep breathing or coughing. Generally, the clinical course of acute bronchitis is self-limited, with complete healing and full return to function typically seen within 10-14 days following symptom onset.

Chronic bronchitis has also been defined as a complex of symptoms that includes cough that lasts more than 1 month or recurrent productive cough that may be associated with wheezing or crackles on auscultation. Elements of these descriptors are present in the working definitions of asthma, as well.

Treatment of chronic bronchitis in pediatric patients includes rest, use of antipyretics, adequate hydration, and avoidance of smoke.

Analgesics and antipyretics target the symptoms of pediatric bronchitis. In chronic cases, bronchodilator therapy should be considered. Oral corticosteroids should be added if cough continues and the history and physical examination findings suggest a wheezy form of bronchitis.

Acute bronchitis begins as a respiratory tract infection that manifests as the common cold. Symptoms often include coryza, malaise, chills, slight fever, sore throat, and back and muscle pain.

The cough in these children is usually accompanied by a nasal discharge. The discharge is watery at first, then after several days becomes thicker and colored or opaque. It then becomes clear again and has a mucoid watery consistency before it spontaneously resolves within 7-10 days. Purulent nasal discharge is common with viral respiratory pathogens and, by itself, does not imply bacterial infection.

Initially, the cough is dry and may be harsh or raspy sounding. The cough then loosens and becomes productive. Children younger than 5 years rarely expectorate. In this age group, sputum is usually seen in vomitus (ie, posttussive emesis). Parents frequently note a rattling sound in the chest. Hemoptysis, a burning discomfort in the chest, and dyspnea may be present.

Brunton et al noted that adult patients with chronic bronchitis have a history of persistent cough that produces yellow, white, or greenish sputum on most days for at least 3 months of the year and for more than 2 consecutive years. Wheezing and reports of breathlessness are also common. Pulmonary function testing in these adult patients reveals irreversible reduction in maximal airflow velocity.

Physical Examination

Lungs may sound normal. Crackles, rhonchi, or large airway wheezing, if any, tend to be scattered and bilateral. The pharynx may be injected.

For maximal cost-effectiveness, diagnostic laboratory tests for bronchitis should be performed in a stepwise manner. Patients with uncomplicated acute respiratory illness who are cared for in an outpatient setting need little, if any, laboratory evaluation.

Testing in Hospitalized Children

For hospitalized children, serum C-reactive protein screen, respiratory culture, rapid diagnostic studies, and serum cold agglutinin testing (at the appropriate age) help to classify whether the infection is caused by bacteria, atypical pathogens (eg, Chlamydia pneumoniae, Mycoplasma pneumoniae), or viruses. Obtain a blood or sputum culture if antibiotic therapy is under consideration.

For the child admitted to the hospital with a possible chlamydial, mycoplasmal, or viral lower respiratory tract infection for which specific therapy is considered, test nasopharyngeal secretions for these pathogens, using antigen or polymerase chain reaction testing for Chlamydia species and respiratory syncytial, parainfluenza, and influenza viruses or viral culture. Results will guide appropriate antimicrobial selection.

For the child who has been intubated, collect a specimen of deep respiratory secretions for Gram stain, chlamydial and viral antigen assays, and bacterial and viral cultures.

Chest Radiography

Chest films generally appear normal in patients with uncomplicated bronchitis. Abnormal findings are minimal and may include atelectasis, hyperinflation, and peribronchial thickening. Focal consolidation is not usually present. These findings are similar to the radiographic findings in patients with asthma. Radiographic findings may help exclude other diseases or complications, particularly when abnormalities in either vital signs or pulse oximetry findings are present.

Pulmonary Function Testing

Pulmonary function tests may show airflow obstruction that is reversible with bronchodilators. Bronchial challenge, such as with exercise or with histamine or methacholine exposure, may demonstrate the airway hyperreactivity characteristic of asthma.

Bronchoscopy

On fiberoptic bronchoscopy, a diagnosis of chronic bronchitis is suggested if the airways appear erythematous and friable. Bronchoalveolar lavage may be useful in establishing an infectious cause. Bronchoalveolar lavage may reveal numerous monocytic or polymorphonuclear inflammatory cells. In children with chronic aspiration of gastric contents, lipids may be present within macrophages.

 

Treatment

Emergency care for acute bronchitis or exacerbation of chronic bronchitis must focus on ensuring that the child has adequate oxygenation. Outpatient care is appropriate unless bronchitis is complicated by severe underlying disease. General measures include rest, use of antipyretics, adequate hydration, and avoidance of smoke.

Proper care of any underlying disorder is of paramount importance. Consideration of asthma and adequate therapy are critical to an early response.

Febrile patients should increase oral fluid intake. Instruct the patient to rest until the fever subsides.

Resolution of symptoms, normal findings on physical examination, and normal pulmonary function test results indicate the end of the need for acute treatment. Patients in whom asthma is diagnosed will likely require ongoing therapy for that disease. Patients with defined hypogammaglobulinemia may need periodic immunoglobulin replacement treatments. These are best coordinated with the assistance of a pediatric allergy and immunology or pulmonary specialist.

 

Medication Summary

In acute bronchitis, medical therapy generally targets symptoms and includes use of analgesics and antipyretics.

In chronic bronchitis, bronchodilator therapy should be considered and instituted; either a beta-adrenergic agonist, such as albuterol or metaproterenol, or theophylline may be effective. Beta-adrenergic agents are less toxic, have a more rapid onset of action than theophylline, and do not require monitoring of levels. Inhaled corticosteroids may be effective.

In the child who continues to cough despite a trial of bronchodilators and in whom the history and physical examination findings suggest a wheezy form of bronchitis, oral corticosteroids should be added. If the response is suboptimal or if fever persists, antibiotic therapy with an agent such as a macrolide or beta-lactamase–resistant antimicrobial may be considered.

Antibiotics should not be the primary therapy. They usually do not result in a cure and may delay the start of more appropriate asthma therapies.

 

Pediatric Bronchiectasis

Background

René Laennec, inventor of the stethoscope, first described bronchiectasis in 1819 while observing patients with tuberculosis and the sequelae of pneumonia in the preantibiotic era. The term bronchiectasis is derived from the Greek bronchion, meaning windpipe, and ektasis, meaning stretched. Bronchiectasis is characterized by the dilatation of bronchi with destruction of elastic and muscular components of their walls.

Bronchiectasis can be focal or diffuse. It is usually due to acute or chronic infection or inflammation, anatomic airway obstruction, or underlying congenital disease that predisposes to chronic infection. The presentation includes recurrent respiratory infections, productive cough, shortness of breath, and occasional hemoptysis. See the images below.

 

Chest radiograph of a child with severe adenoviral pneumonia as an infant. The child has persistent symptoms of cough, congestion, and wheezing.

In developing countries, bronchiectasis is still frequently encountered as one of the sequelae of acute infection. In the developed world, immunizations and antibiotics have led to a declining incidence of this disorder. In these countries, diffuse bronchiectasis is more often found in association with underlying disorders such as cystic fibrosis (CF), immune deficiencies (including human immunodeficiency virus [HIV] infection), primary ciliary dyskinesia, and recurrent aspiration syndromes. Focal bronchiectasis is usually associated with bronchial obstruction (ie, from a foreign body) that leads to infection.

Non–cystic fibrosis (CF) bronchiectasis in children presents as a wide spectrum of disease severity. Some children have intermittent symptoms of cough and occasional lower respiratory tract infections. Others experience daily cough and produce purulent fetid sputum, requiring frequent hospitalizations for respiratory exacerbations.

Because bronchiectasis is defined as an abnormal dilatation of airways, the diagnosis depends on radiographically or anatomically visualizing the typical changes. In patients with suspected bronchiectasis without characteristic chest radiograph findings, a high-resolution computed tomography (HRCT) scan is the diagnostic procedure of choice. Other testing may be indicated to diagnose underlying conditions.

Cough is an almost universal symptom and is frequently described as productive in older children or loose in toddlers and infants. In addition to the treatment of any identified underlying disorder in patients with bronchiectasis, therapy is guided at reducing the airway secretions and facilitating their removal through cough. Pharmacotherapy may be used to enhance bronchodilation and to improve mucociliary clearance. Antibiotics can be used to prevent and treat recurrent infections. Secretions can be mobilized with chest physiotherapy and mucolytic agents. Occasionally, surgery may be considered.

This article focuses on children with non-CF bronchiectasis. See Cystic Fibrosis for a more in-depth discussion of CF bronchiectasis and Bronchiectasis for a discussion of this disorder in adults.

 

Pathophysiology

Bronchiectasis generally results from obstruction and/or inflammation of the airway. The obstruction and inflammation may be due to any of the underlying disorders listed above or to infection with acute tuberculosis, adenovirus, measles, Mycobacteriumavium, or Aspergillus fumigatus.

Chronic infection can lead to recruitment of neutrophils, T lymphocytes, and monocyte-derived cytokines. The release of inflammatory mediators, elastases, and collagenases leads to inflammation and destruction of elastic and muscular components of bronchial walls. In addition, the outward elastic recoil forces of surrounding lung parenchyma exert traction, which causes expansion of airway diameter. These changes may be accompanied by bronchial arterial proliferation, which predisposes to hemoptysis. Hemoptysis may also occur as a result of the dilating airways impinging on the accompanying blood vessels.

Bronchiectasis associated with bronchial obstruction may have a focal distribution distal to the site of obstruction. Bronchiectasis associated with underlying disease is likely to be diffuse.

Two different types of bronchiectasis are noted: cylindrical, which is presumably more readily reversible if the underlying disorder can be controlled, and saccular, which is less readily reversible even if the underlying disorder is controlled.

 

Etiology

Bronchiectasis may result from infection, congenital or acquired disorders, or obstruction. All causes share the same pathophysiologic pathway: ineffective pulmonary toilet and chronic or recurrent infection and inflammation.

Common infectious causes include the following:

• Severe pneumonia, especially viral

• Measles, tuberculosis, pertussis, Adenovirus Mycobacterium avium, and Aspergillus fumigatus infections

• HIV infection: Children who develop lymphocytic interstitial pneumonitis seem at increased risk of subsequent bronchiectasis

Congenital disorders associated with bronchiectasis include the following:

• CF

• Young syndrome

• Ciliary dyskinesia

• Marfan syndrome

• Bruton agammaglobulinemia

• Congenital absence of bronchial muscle (Mounier-Kuhn syndrome) or cartilage (Williams-Campbell syndromes)

• Immunoglobulin A (IgA) and G (IgG) deficiencies and IgG subclass deficiencies, especially IgG2 deficiency

Acquired disorders associated with bronchiectasis include the following:

• Intrinsic airway luminal obstruction by a retained bronchial foreign bodyor extrinsic compression by mass

• Chronic aspiration, which is associated with swallowing dysfunction, gastroesophageal reflux disease, or tracheoesophageal fistula

• Connective tissue disorders, including rheumatoid arthritis and systemic lupus erythematosus

• Allergic bronchopulmonary aspergillosis

• Tracheal stenosis with impaired mucociliary clearance

• Severe tracheomalacia or bronchomalacia with impairment of mucociliary clearance

• Fibrosing lung diseases associated with sarcoidosis or idiopathic pulmonary fibrosis

• Persistent atelectasis

 

Epidemiology

United States statistics

Current population-based estimates of occurrence are not available. In 1963, Clark estimated an incidence of 1.06 cases per 10,000 population.The incidence of bronchiectasis associated with underlying systemic disease reflects the incidence of the particular disease. The most common congenital disease associated with bronchiectasis is CF. One study estimates that 110,000 people in the United States have bronchiectasis, including adults.

Callahan and associates reported the incidence among Alaskan Native children in the Yuskon-Kuskokwim region to be about 140 cases per 10,000 population.Redding and colleagues reported the incidence of bronchiectasis in southwest Alaskan Natives is 16 cases per 1,000 population.

 

International statistics

In developed countries, the frequency is similar to that in the United States. The frequency is higher in the developing world, where measles, adenovirus infection, pneumonia, tuberculosis, and HIV infection are all on the rise and are associated with bronchiectasis.

In a study from the United Kingdom that started in 1949, Field studied children with bronchiectasis for almost 2 decades and documented a fall in the annual hospitalization rate for bronchiectasis in 5 British hospitals. During the study period, as broad-spectrum antibiotics became widely available, the hospitalization rate decreased from approximately 48 cases per 10,000 population to 10 cases per 10,000 population.

In New Zealand, Twiss and colleagues reported the incidence of bronchiectasis in children younger than 15 years at 3.7 cases per 100,000 population in 2001-2002.The incidence was highest among Pacific children, at 17.8 cases per 100,000 population. The incidence was 4.8 cases per 100,000 population in Maori children and 1.5 cases per 100,000 in New Zealand overall, compared with 2.4 cases per 100,000 in other Pacific regions. Most New Zealand children with bronchiectasis developed disease in early childhood and had a delayed diagnosis.

Twiss and colleagues noted that the incidence of bronchiectasis in New Zealand children was nearly twice the rate of CF and 7 times that of bronchiectasis in Finland, which is the only other country reporting a childhood national rate. They further noted that in central Australian aborigines, the incidence is 14 cases per 1,000 population, compared with 0.1 cases per 1,000 in Scotland and 4.9 cases per 1,000,000 in Finnish children.

 

Race-, sex-, and age-related demographics

Bronchiectasis is more common in patients of Polynesian and Alaskan Native ancestry. Karadag and associates’ study in Turkey suggests possible genetic predisposition in some populations and found that 43% of children with bronchiectasis had parents who were first-degree or second-degree relatives but presumably without any other known underlying disorder.

Morrissey and colleagues found non-CF bronchiectasis to be more common and more virulent in women. The differences may results from inflammatory-immune, environmental, anatomic, or other genetic factors.

Karadag and colleagues reported a mean age at presentation of 7.4 ± 3.7 years.In Field’s 1949 survey, 15% of patients presented when younger than 2 years, 43% when aged approximately 2 years, and 92% when younger than 10 years.These data predate most current immunizations and antibiotics. In Clark’s 1963 series, one half of the children developed symptoms when younger than 3 years.

 

Prognosis

Overall, the prognosis is good for a child with bronchiectasis. The key to a successful outcome is determining whether the cause of the damage is ongoing (eg, chronic aspiration) and then treating the underlying problem.

Growth of new pulmonary tissue in children proceeds rapidly until about age 6 years and then tapers off through childhood. Injury at an early age may be compensated for by growth of normal healthy lungs in the absence of ongoing damage.

In the absence of an underlying condition, children with isolated bronchiectasis often have a good prognosis. Progressive bronchiectasis from underlying disease (eg, CF) or ongoing pulmonary insult (eg, aspiration syndromes) causes a progressive obstructive defect and, ultimately, respiratory compromise. This may manifest as dyspnea at rest or with exercise or sleep-disordered breathing. Ultimately, patients may experience chronic hypoxemia, pulmonary hypertension, cor pulmonale, hypercarbia, respiratory failure, and death.

Progressive focal disease may lead to progressive infection with fever and abnormal growth. The area may contribute enough ventilation/perfusion mismatch to cause hypoxemia with exercise. Although not yet proven, infected secretions from the abnormal portion of the lung could spill over to other portions of the lung, causing more widespread infection.

Prolonged therapy with systemic or high-dose inhaled corticosteroids may affect growth and increase the risk of other complications of steroids. In patients with non-CF bronchiectasis, prolonged systemic antibiotics may produce a small benefit and reduce sputum volume and purulence but may also be associated with unpleasant side effects.

Karadag and associates illustrated that bronchiectasis remains one of the most common causes of childhood morbidity in developing countries.Twiss and colleagues recently demonstrated that children with bronchiectasis have significant airway obstruction that deteriorates over time.However, Karadag and associates demonstrated that children with non-CF bronchiectasis have a much slower decline in lung function than children with CF.Akalin and colleagues reported decreased left ventricular function and exercise capacity in bronchiectasis.

Limited mortality data are available. In Field’s original group, who were studied at the beginning of the antibiotic era, 4% of children with medically treated bronchiectasis died (mostly from infection), and 3% of children who were surgically treated died (many immediately following or as a late result of surgery) in the ensuing 2 decades.

 

Pneumonia

Pneumonia and other lower respiratory tract infections are the leading causes of death worldwide. Because pneumonia is common and is associated with significant morbidity and mortality, properly diagnosing pneumonia, correctly recognizing any complications or underlying conditions, and appropriately treating patients are important. Although in developed countries the diagnosis is usually made on the basis of radiographic findings, the World Health Organization (WHO) has defined pneumonia solely on the basis of clinical findings obtained by visual inspection and on timing of the respiratory rate.

Pneumonia may originate in the lung or may be a focal complication of a contiguous or systemic inflammatory process. Abnormalities of airway patency as well as alveolar ventilation and perfusion occur frequently due to various mechanisms. These derangements often significantly alter gas exchange and dependent cellular metabolism in the many tissues and organs that determine survival and contribute to quality of life. Recognition, prevention, and treatment of these problems are major factors in the care of children with pneumonia.

One particular form of pneumonia present in the pediatric population, congenital pneumonia, presents within the first 24 hours after birth. For more information

Other respiratory tract diseases such as croup (laryngotracheobronchitis), bronchiolitis, and bronchitis are beyond the scope of this article and are not discussed further.

 

Diagnosis

The signs and symptoms of pneumonia are ofteonspecific and widely vary based on the patient’s age and the infectious organisms involved.

Observing the child’s respiratory effort during a physical exam is an important first step in diagnosing pneumonia. The World Health Organization (WHO) respiratory rate thresholds for identifying children with pneumonia are as follows:

·        Children younger than 2 months: Greater than or equal to 60 breaths/min

·        Children aged 2-11 months: Greater than or equal to 50 breaths/min

·        Children aged 12-59 months: Greater than or equal to 40 breaths/min

Assessment of oxygen saturation by pulse oximetry should be performed early in the evaluation when respiratory symptoms are present. Cyanosis may be present in severe cases. Capnography may be useful in the evaluation of children with potential respiratory compromise.

Other diagnostic tests may include the following:

·        Auscultation by stethoscope:

The sine qua non for pneumonia has always been the presence of crackles or rales. Although often present, focal crackles as a stand-alone physical examination finding is neither sensitive nor specific for the diagnosis of pneumonia. Additionally, not all children with pneumonia have crackles.

Rales, rhonchi, and cough are all observed much less frequently in infants with pneumonia than in older individuals. If present, they may be caused by noninflammatory processes, such as congestive heart failure, condensation from humidified gas administered during mechanical ventilation, or endotracheal tube displacement. Although alternative explanations are possible, these findings should prompt careful consideration of pneumonia in the differential diagnosis.

Other examination findings suggestive of pneumonia include asymmetry of breath sounds in infants, such as focal wheezing or decreased breath sounds in one lung field, and asymmetry of chest excursions, which suggest air leak or emphysematous changes secondary to partial airway obstruction. Similarly, certain more diffuse lung infections (eg, viral infections) may result in generalized crackles or wheezing.

·        Cultures:

In general, blood culture results are positive in 10-15% of patients with pneumococcal pneumonia. The percentage is even less in patients with Staphylococcus infection. However, a blood culture is still recommended in complicated cases of pneumonia. It may be the only way to identify the pathogen and its antimicrobial susceptibility patterns.

·        Serology:

Because of the relatively low yield of cultures, more efforts are under way to develop quick and accurate serologic tests for common lung pathogens, such as M pneumoniae, Chlamydophila species, and Legionella.

·        Complete blood cell count (CBC):

Testing should include a CBC count with differential and evaluation of acute-phase reactants (ESR, CRP, or both) and sedimentation rate. The total white blood cell (WBC) count and differential may aid in determining if an infection is bacterial or viral, and, together with clinical symptoms, chest radiography, and ESR can be useful in monitoring the course of pneumonia. In cases of pneumococcal pneumonia, the WBC count is often elevated.

·        Chest radiography:

Chest radiography is indicated primarily in children with complications such as pleural effusions and in those in whom antibiotic treatment fails to elicit a response. Computed tomography (CT) scanning of the chest and ultrasonography are indicated in children with complications such as pleural effusions and in those in whom antibiotic treatment fails to elicit a response.

·        Ultrasonography

New data show that point-of-care ultrasonography accurately diagnoses most cases of pneumonia in children and young adults. Ultrasonography may eventually replace x-rays for diagnosis.

Management

Initial priorities in children with pneumonia include the identification and treatment of respiratory distress, hypoxemia, and hypercarbia. Grunting, flaring, severe tachypnea, and retractions should prompt immediate respiratory support. Children who are in severe respiratory distress should undergo tracheal intubation if they are unable to maintain oxygenation or have decreasing levels of consciousness. Increased respiratory support requirements such as increased inhaled oxygen concentration, positive pressure ventilation, or CPAP are commonly required before recovery begins.

Antibiotics

The majority of children diagnosed with pneumonia in the outpatient setting are treated with oral antibiotics. High-dose amoxicillin is used as a first-line agent for children with uncomplicated community-acquired pneumonia. Second- or third-generation cephalosporins and macrolide antibiotics such as azithromycin are acceptable alternatives. Combination therapy (ampicillin and either gentamicin or cefotaxime) is typically used in the initial treatment of newborns and young infants.

Hospitalized patients are usually treated with an advanced-generation intravenous cephalosporin, often in combination with a macrolide. Children who are toxic appearing should receive antibiotic therapy that includes vancomycin (particularly in areas where penicillin-resistant pneumococci and methicillin-resistant S aureus [MRSA] are prevalent) along with a second- or third-generation cephalosporin.

Vaccines

Aside from avoiding infectious contacts (difficult for many families who use daycare facilities), vaccination is the primary mode of prevention. Influenza vaccine is recommended for children aged 6 months and older. The pneumococcal conjugate vaccine (PCV13) is recommended for all children younger than 59 months old. The 23-valent polysaccharide vaccine (PPVSV) is recommended for children 24 months or older who are at high risk of pneumococcal disease.

 

Pediatric Airway Foreign Body

Background

The human body has numerous defense mechanisms to keep the airway free and clear of extraneous matter. These include the physical actions of the epiglottis and arytenoid cartilages in blocking the airway, the intense spasm of the true and false vocal cords any time objects come near the vocal cords, and a highly sensitive cough reflex with afferent impulses generated throughout the larynx, trachea, and all branch points in the proximal tracheobronchial tree. However, none of these mechanisms is perfect, and foreign bodies frequently lodge in the airways of children.

Often, the child presents after a sudden episode of coughing or choking while eating with subsequent wheezing, coughing, or stridor. However, iumerous cases, the choking episode is not witnessed, and, in many cases, the choking episode is not recalled at the time the history is taken.

The most tragic cases occur when acute aspiration causes total or near-total occlusion of the airway, resulting in death or hypoxic brain damage.

The more difficult cases are those in which aspiration is not witnessed or is unrecognized and, therefore, is unsuspected.

In these situations, the child may present with persistent or recurrent cough, wheezing, persistent or recurrent pneumonia, lung abscess, focal bronchiectasis, or hemoptysis.

If the material is in the subglottic space, symptoms may include stridor, recurrent or persistent croup, and voice changes.

In one series, as many as one third of parents were unaware of the aspiration or remembered an event that occurred more than a week before the presentation.In as many as 25% of cases, aspiration occurred more than one month before presentation. Consequently, a high index of suspicion in addition to the history may be necessary to reach the diagnosis. In another series of 280 foreign body aspirations, 47% were detected more than 24 hours after the aspiration.However, 99% had signs or symptoms or abnormal plain radiographs before the bronchoscopy.

One of the author’s cases involved a 9-year-old boy with persistent pneumonia and lung abscess. Upon bronchoscopy, a plastic toy was visualized in his left lower lobe bronchus. Neither he nor his family could recognize the toy and had no idea how long it had been since it might have been aspirated.

Physical

·        Major findings include new abnormal airway sounds, such as wheezing, stridor, or decreased breath sounds. These sounds are often, but not always, unilateral.

·        Sounds are inspiratory if the material is in the extrathoracic trachea. If the lesion is in the intrathoracic trachea, noises are symmetric but sound more prominent in the central airways. These sounds are a coarse wheeze (sometimes referred to as expiratory stridor) heard with the same intensity all over the chest.

·        Once the foreign body passes the carina, the breath sounds are usually asymmetric. However, remember that the young chest transmits sounds very well, and the stethoscope head is often bigger than the lobes. A lack of asymmetry should not dissuade the observer from considering the diagnosis.

·        Similarly, a lack of findings upon physical examination does not preclude the possibility of an airway foreign body.

Radiography:

Most aspirated foreign bodies are food material and are radiolucent. Thus, one has to look indirectly for signs of the foreign body.

Aspirated foreign body (backing to an earring) lodged in the right main stem bronchus.

Fluoroscopy:

Fluoroscopy of the chest may be helpful in showing focal air trapping, paradoxical diaphragmatic motion, or both.

CT scanning:

Chest CT scanning may reveal the material in the airway, focal airway edema, or focal overinflatioot detected using plain radiography. Even if no foreign body is evident on any of the radiographic studies, a foreign body may still be present, and a bronchoscopy should be performed if the suspicion is high.

Procedures

Bronchoscopy

If the history and physical findings are diagnostic, no workup is needed. The child should immediately be referred for rigid bronchoscopy. Although a flexible bronchoscopy is useful in detecting a foreign body, removing most foreign bodies using the currently available flexible bronchoscopes and their attachments is difficult. However, removal using a fiberoptic bronchoscope has been reported.

If the possiblity of foreign body is significant but has not been diagnosed by phyical examination or radiographic studies, flexible bronchoscopy should be strongly considered.

Heimlich maneuver

If the child has respiratory distress and is unable to speak or cry, complete airway obstruction is probable, and the likelihood of morbidity or mortality is high. In those cases, a Heimlich maneuver may be performed. If the child is able to speak, the Heimlich maneuver is contraindicated because it might dislodge the material to an area where it could cause complete airway obstruction.

Medical Care

·        Bronchodilators and corticosteroids should not be used to remove the foreign body, and chest physical therapy with postural drainage may dislodge the material to an area where it may cause more harm, such as at the level of the vocal cords.

·        Medications are not necessary before removal, although the endoscopist may observe enough focal swelling after the material is removed to recommend a short course of systemic corticosteroids.

·        Unless the airway secretions are infected with organisms present, antibiotics are not necessary.

Surgical Care

·        Surgical therapy for an airway foreign body involves endoscopic removal, usually with a rigid bronchoscope.

Consultations

·        If the diagnosis is in question or a flexible bronchoscopy is needed, a pediatric pulmonologist should be consulted.

·        A pediatric surgeon or pediatric otolaryngologist usually performs the rigid bronchoscopy if necessary.

Medication Summary

No medications are needed. If significant swelling is observed in the airway or if granulation tissue is present, a corticosteroid (eg, prednisolone, prednisone) may be administered. Unless airway secretions are infected, antibiotics are not helpful or necessary.

 

Asthma

Asthma is a chronic inflammatory disorder of the airways characterized by an obstruction of airflow. Among children and adolescents aged 5-17 years, asthma accounts for a loss of 10 million school days annually and costs caretakers $726.1 million per year because of work absence.

Essential update: BPA exposure and risk of childhood asthma

Results of a prospective birth cohort study of 568 women in the third trimester of pregnancy showed postnatal bisphenol A (BPA) exposure was associated with significantly increased risk for wheeze and asthma in offspring at ages 3, 5, and 7 years. Investigators measured urine BPA concentrations in mothers and their children to estimate BPA exposure. After adjusting for secondhand smoke exposure and other asthma risk factors, postnatal BPA exposure was associated with a 40% to 50% increased risk for wheeze and asthma. The study also found that exposure during the third trimester was inversely associated with risk for wheeze at age 5.

Signs and symptoms

The clinician should establish whether the patient has any of the following symptoms:

·        Wheezing: A musical, high-pitched whistling sound produced by airflow turbulence is one of the most common symptoms of asthma

·        Cough: Usually, the cough is nonproductive and nonparoxysmal; coughing may be present with wheezing

·        Cough at night or with exercise: Coughing may be the only symptom of asthma, especially in cases of exercise-induced or nocturnal asthma; children with nocturnal asthma tend to cough after midnight, during the early hours of morning

·        Shortness of breath

·        Chest tightness: A history of tightness or pain in the chest may be present with or without other symptoms of asthma, especially in exercise-induced or nocturnal asthma

Sputum production

In an acute episode of asthma, symptoms vary according to the episode’s severity. Infants and young children suffering a severe episode display the following characteristics:

·        Breathless during rest

·        Not interested in feeding

·        Sit upright

·        Talk in words (not sentences)

·        Usually agitated

With imminent respiratory arrest, the child displays the aforementioned symptoms and is also drowsy and confused. However, adolescents may not have these symptoms until they are in frank respiratory failure.

Physical examination

Findings during a severe episode include the following:

·        Respiratory rate is often greater than 30 breaths per minute

·        Accessory muscles of respiration are usually used

·        Suprasternal retractions are commonly present

·        The heart rate is greater than 120 beats per minute

·        Loud biphasic (expiratory and inspiratory) wheezing can be heard

·        Pulsus paradoxus is often present (20-40 mm Hg)

·        Oxyhemoglobin saturation with room air is less than 91%

Findings in status asthmaticus with imminent respiratory arrest include the following:

·        Paradoxical thoracoabdominal movement occurs

·        Wheezing may be absent (in patients with the most severe airway obstruction)

·        Severe hypoxemia may manifest as bradycardia

·        Pulsus paradoxus may disappear: This finding suggests respiratory muscle fatigue

Diagnosis

Tests used in the diagnosis of asthma include the following:

·        Pulmonary function tests: Spirometry and plethysmography

·        Exercise challenge: Involves baseline spirometry followed by exercise on a treadmill or bicycle to a heart rate greater than 60% of the predicted maximum, with monitoring of the electrocardiogram and oxyhemoglobin saturation

·        Fraction of exhaled nitric oxide (FeNO) testing: Noninvasive marker of airway inflammation

·        Radiography: Reveals hyperinflation and increased bronchial markings; radiography may also show evidence of parenchymal disease, atelectasis, pneumonia, congenital anomaly, or a foreign body

·        Allergy testing: Can identify allergic factors that may significantly contribute to asthma

·        Histologic evaluation of the airways: Typically reveal infiltration with inflammatory cells, narrowing of airway lumina, bronchial and bronchiolar epithelial denudation, and mucus plugs

Management

Guidelines from the National Asthma Education and Prevention Program emphasize the following components of asthma care:

·        Assessment and monitoring: In order to assess asthma control and adjust therapy, impairment and risk must be assessed; because asthma varies over time, follow-up every 2-6 weeks is initially necessary (when gaining control of the disease), and then every 1-6 months thereafter

·        Education: Self-management education should focus on teaching patients the importance of recognizing their own level of control and signs of progressively worsening asthma symptoms; educational strategies should also focus on environmental control and avoidance strategies, as well as on medication use and adherence (eg, correct inhaler techniques and use of other devices)

·        Control of environmental factors and comorbid conditions

·        Pharmacologic treatment

·        Pharmacologic treatment

Pharmacologic asthma management includes the use of agents for control and agents for relief. Control agents include the following:

·        Inhaled corticosteroids

·        Inhaled cromolyn or nedocromil

·        Long-acting bronchodilators

·        Theophylline

·        Leukotriene modifiers

·        Anti-immunoglobulin E (IgE) antibodies (omalizumab)

Relief medications include the following:

·        Short-acting bronchodilators

·        Systemic corticosteroids

·        Ipratropium

 

Aspiration Syndromes 

 

Background

Aspiration syndromes include all conditions in which foreign substances are inhaled into the lungs. Most commonly, aspiration syndromes involve oral or gastric contents associated with gastroesophageal reflux (GER), swallowing dysfunction, neurological disorders, and structural abnormalities. The volume of refluxate may be significant, usually causing acute symptoms associated with the penetration of gastric contents into airways, or there may be episodic incidents of small amounts of oral or gastric reflux or saliva that enter the airways causing intermittent or persistent symptoms.

GER is very common in infants and children and has been associated with a spectrum of pediatric problems; however, the percentage of reflux that causes respiratory complications is unknown. In 1912, Sir William Osler described the relationship between asthma and GER by stating that “attacks may be due to direct irritation of the bronchial mucosa or… indirectly, too, by reflex influences from stomach.” Recent literature describes GER and aspiration syndromes as common occurrences with increasing diagnostic rates. Swallowing dysfunction in conjunction with GER is more likely to cause respiratory symptoms than GER symptoms alone. Eosinophilic GI disorders (eg, eosinophilic esophagitis, gastroenteritis) may also manifest similarly to GER but are refractory to traditional reflux therapies.

Guidelines for evaluation and treatment of GER in infants and children can be found at The North American Society for Pediatric Gastroenterology.

Swallowing dysfunction is a known etiology of aspiration in children. Divided into 4 distinct phases, swallowing is a complex action that involves 5 cranial nerves and 26 muscles. The mouth, pharynx, larynx, and esophagus are involved in a coordinated effort to induce swallowing. Any anatomic, neurologic, or physiologic defect in the swallowing mechanism may lead to aspiration.

Cricopharyngeal dysfunction, cricopharyngeal incoordination of infancy, and transient pharyngeal muscle dysfunction are well described in the pediatric literature. Cricopharyngeal dysfunction involves cricopharyngeal muscle spasm or achalasia of the superior esophageal sphincter. Cricopharyngeal incoordination of infancy is noted in infants who have a normal suck reflex but have incoordination during swallowing; this is possibly secondary to delayed maturation of swallowing reflexes or may be associated with cerebral palsy.

Neurological disorders, including congenital and progressive diseases, may manifest as aspiration syndromes in infants and children. Isolated superior laryngeal nerve damage, vocal cord paralysis, cerebral palsy, muscular dystrophy, and Riley-Day syndrome (i.e., familial dysautonomia) are a few of the neurological disorders associated with increased risk of aspiration.

Anatomic disorders, such as cleft palate, esophageal atresia, tracheoesophageal fistula, duodenal obstruction, or malrotation, may have associated aspiration risk. Other conditions such as macroglossia, micrognathia, and laryngeal cleft may predispose patients to aspiration. Motility disorders, such as achalasia or connective-tissue disorders, are associated with increased risk of aspiration.

 

Pathophysiology

Studies in humans and animal models revealed that aspiration of acidic content (pH < 2.5) into the lungs causes mucosal desquamation, damage to alveolar lining cells and capillaries, and acute neutrophil inflammation.

Epidemiology

Frequency

United States

Medical practitioners are diagnosing GER and its respiratory complications more frequently now than in the past. Theories of the increased frequency of GER diagnosis include an increased prevalence of pathologic GER, improvement in diagnostic tests for GER, misdiagnosis, and overdiagnosis. The increase in diagnostic rate probably is multifactorial, but factors such as formula feeding, increased volume of feeds, and prolonged use of infant seating devices in infants too young to sit have been suggested as epidemiologic causes for this increase.

In a study of the diagnostic rate of GER in Army hospitals over a 25-year period (1971-1995), the total diagnoses of GER increased 20-fold, with 84% of cases in infants younger than 6 months. The diagnostic rate for GER diagnosis rose from 0.74 in 1000 persons in 1971 to 8.16 in 1000 persons in 1995. Orenstein states that 40% of healthy infants regurgitate more than once a day, and as many as 20% of children reflux to the extent that parents feel it is a problem. Nelson et al (1998) described that most infants outgrow this physiologic reflux but that as many as 5% of infants have persistent reflux symptoms.

Approximately 7% of infants have reflux severe enough to be brought to a physician’s attention. As many as 40-50% of infants with GER present with respiratory symptoms. Approximately 25-80% of children with asthma have GER, but as many as one third of patients with pulmonary symptoms of GER have no esophageal symptoms.

Incidence of eosinophilic GI disorders has increased during the past decade. Eosinophilic esophagitis has been diagnosed in approximately 2 of 10,000 children in the Cincinnati region. Another group of investigators noted that 1% of patients with esophagitis have eosinophilic esophagitis.

The incidence of swallowing dysfunction associated with aspiration syndromes is not known because clinical signs of aspiration may be quite subtle. As many as 70% of patients with pharyngeal dysphagia with aspiration have silent aspiration (ie, no overt clinical signs during aspiration).

The incidence of aspiration syndromes associated with anatomic or neurologic disorders is unknown. The incidence of an isolated cleft palate is approximately 0.5 per 1000 live births, whereas the incidence of cleft lip and palate differs by ethnicity. Patients with a cleft palate are at risk for aspiration secondary to an abnormal communication with the nasal and oral cavities. Nasopharyngeal reflux commonly is observed in patients with cleft palate with or without associated cleft lip. Unilateral or bilateral vocal cord paralysis accounts for approximately 10% of all congenital laryngeal lesions. Esophageal atresia occurs in 1 per 3000-4000 live births, with 85% associated with tracheoesophageal fistulas.

International

International data on frequency of aspiration syndromes are not available.

 

Mortality/Morbidity

Patients with an aspiration syndrome are at risk for severe respiratory sequelae and, possibly, death. Patients with a massive aspiration event have a mortality rate of 25%. One study by Kohda et al examined 72 infants with documented aspiration by fluoroscopy for etiology of the aspiration and prognosis. None of the patients without underlying neurologic disorders had evidence of aspiration after one year. In patients with neurological disorders, two thirds of patients had prolonged aspiration on follow-up. In patients who initially presented with a near-miss sudden infant death syndrome, or acute life-threatening episode (ALTE), 3 of 13 patients had prolonged aspiration.

No standard case definition of GER disease is recognized; thus, morbidity statistics are difficult to interpret. In 1959, Carre studied the natural history of severe GER and found that less than 5% of clinically affected patients died as a consequence of reflux.

 

Race

In whites, cleft lip and palate occurs in approximately 1 in 1000 births; in Asians, it occurs in approximately 2 in 1000 births. In blacks, the incidence of cleft lip and palate is approximately 0.41 in 1000 births.

 

Sex

One study revealed an increased incidence of GER in males over females, but no strong prevalence in one sex has been observed. Cleft lip and palate are seen more commonly in males than in females, with approximately 60-80% incidence in males. Isolated cleft palates occur more frequently in females.

 

Age

Physiologic GER (ie, benign regurgitation) occurs most commonly in the first few months of life but generally resolves by age 1-2 years. Approximately 84% of patients diagnosed with GER in Army hospitals in a 25-year period were younger than 6 months.[5] Patients with anatomic, physiologic, or neurologic disorders associated with aspiration are often diagnosed early. Esophageal atresia with or without tracheoesophageal fistula may be diagnosed in the delivery room or shortly after birth. The prevalence of respiratory complications of GER in infants and children by age is not known.

 

Childhood Sleep Apnea 

 

Background

Childhood obstructive sleep apnea (OSA) syndrome is characterized by episodic upper airway obstruction that occurs during sleep. The airway obstruction may be complete or partial. Three major components of obstructive sleep apnea have been identified: episodic hypoxia, intermittent hypercapnia, and sleep fragmentation. Habitual snoring without obstructive sleep apnea is more common and may also lead to sleep fragmentation. Both primary snoring and obstructive sleep apnea have been associated with poor quality of life and increased health care use in children.

Obstructive sleep apnea syndrome was described more than a century ago, but obstructive sleep apnea in children was first described in the 1970s. It is a common but underdiagnosed condition in children that may ultimately lead to substantial morbidity if left untreated.

The mechanisms of obstruction, adverse effects of obstructive sleep apnea, diagnostic criteria, and recommended treatment options are different in children from those in adults (see the image below). Important recent advances in the understanding of the underlying pathophysiological mechanisms of obstructive sleep apnea in children have been coupled with improved approaches to the diagnosis and management of obstructive sleep apnea.

Go to Obstructive Sleep Apnea for complete information on this topic.

Medical complications associated with obstructive sleep apnea in children.

 

Pathophysiology

Disordered breathing during sleep is a hallmark of obstructive sleep apnea syndrome. Breathing abnormalities include apnea (cessation of air flow) and hypopnea (decreased air flow). In addition, in contrast to adults, some children exhibit a variation of obstructive sleep apnea termed obstructive hypoventilation (OH). Children with obstructive hypoventilation demonstrate periods of hypercapnia that occur in the absence of discrete respiratory events that fulfill the criteria for apnea or hypopnea.

 

Apneas and hypopneas

Physiologic recording methods can differentiate the types of apnea. During obstructive apnea, an individual makes respiratory efforts, but no airflow occurs because of upper airway obstruction. Central apnea is an interruption in both airflow and breathing effort. Mixed apneas have both central and obstructive components. A typical mixed event begins with a central apnea, which is followed immediately by one or more obstructed breaths.

Hypopneas are episodes of shallow breathing during which airflow is decreased by at least 50%. They are usually accompanied by some degree of oxygen desaturation, which can be minor and transient. Like apnea, hypopnea is subdivided into obstructive, central, and mixed. Obstructive hypopneas are episodes of partial upper airway obstruction. Respiratory efforts occur, but airflow is reduced. In central hypopnea, breathing effort and airflow are both decreased. Mixed hypopneas have both central and obstructive components.

In adults, episodes of disordered breathing must last 10 seconds or more before being considered an apnea or hypopnea. Normal resting respiratory rates in children are faster than those in adults, and children have a smaller functional residual capacity and a more compliant chest wall. As a result, children undergo oxygen desaturation more rapidly than adults whenever airflow is interrupted. A definition of apnea or hypopnea requiring that an event last 10 seconds or more before being considered significant is somewhat arbitrary and does not take into account the physiologic differences between adults and children. Consequently, pediatric sleep centers use different duration criteria for labeling events such as apnea or hypopnea. In children, if obstruction occurs with 2 or more consecutive breaths, the event can be called an apnea or hypopnea, even if it lasts less than 10 seconds.

 

Upper airway obstruction

The ability to maintain upper airway patency during the normal respiratory cycle is the result of a delicate equilibrium between the forces that promote airway closure and dilation. This “balance of forces” concept was initially proposed by 2 independent groups and reflects the current line of thought regarding the underlying pathophysiological mechanisms that result in the clinical spectrum of obstructive apnea.

The 4 major predisposing factors for upper airway obstruction are the following:

·        Anatomic narrowing

·        Abnormal mechanical linkage between airway dilating muscles and airway walls

·        Muscle weakness

·        Abnormal neural regulation

Obstructive apnea and hypopnea are related to upper airway obstruction. Upper airway obstruction may occur at one or more levels, including the nasopharynx (area from the nose to the hard palate), mouth, velopharynx (space behind the palate), retroglossal region (area behind the tongue), hypopharynx (region between the tongue base and larynx), and larynx.

The upper airway is a pliant tube whose sidewalls consist of muscle and other soft tissues. During wakefulness, neural input to a number of small muscle groups in the pharynx maintains muscle tone and airway patency. With sleep, an increased resistance to airflow normally accompanies muscular relaxation of these muscle groups. Although most people compensate for these changes, individuals with certain anatomic problems have repeated episodes of partial or complete upper airway obstruction when they sleep.

Childhood sleep apnea differs from adult obstructive sleep apnea in that adults with sleep apnea frequently present with hypersomnia, whereas children often demonstrate short attention spans, emotional lability, and behavioral problems. Obesity is a major risk factor in both adults and children. Fatty infiltration of the pharyngeal soft tissues narrows the caliber of the upper airway and contributes to airway resistance. Although obesity plays a role in some cases of childhood sleep apnea, the airway obstruction is usually related to tonsillar hypertrophy, adenoid hypertrophy, or craniofacial abnormalities. Children with some types of neuromuscular disease (eg, Duchenne muscular dystrophy, spinal muscular atrophy, cerebral palsy) may also have a higher risk of developing sleep apnea.

 

Anatomic narrowing

At any point in life, a smaller cross-sectional area of the upper airway is associated with decreased ability to maintain upper airway patency. In adults, the upper airway behaves as predicted by the Starling resistor model. According to this model, under conditions of flow limitation, maximal inspiratory flow is determined by the pressure changes upstream (nasal) to a collapsible site of the upper airway, and flow is independent of downstream (tracheal) pressure generated by the diaphragm. Pressures at which the airway collapses have been termed critical closing pressures, or Pcrit. In other words, in the presence of a collapsible segment of the upper airway, such as the pharyngeal introitus, the overall resistance to airflow proximal to that segment is the major factor responsible for occlusion of the collapsible segment. This model explains why, for example, snoring and obstructive apnea worsen during a common cold (increased nasal-upstream resistance).

The validity of this model was also confirmed in children, and interestingly, the collapsibility of the upper airway in children was reduced when compared with that of adults. As predicted by the Starling resistor model, the collapsible segment of the upper airway in children displayed less negative (higher and, therefore, more collapsible) pressures in children with obstructive sleep apnea. Components that affect the upstream segment pressures or increase Pcrit are of major consequence to the ability to maintain airway patency. For example, a viral cold or allergic rhinitis that induces increased secretion in the nasal passages and mucosal swelling is associated with increased nasal resistance to airflow. Not surprisingly, the magnitude of snoring and the severity of obstructive apnea are increased during periods in which the upstream segment pressure has been adversely affected.

The contribution of the various anatomical nasopharyngeal structures to Pcrit and the interactions between these structures that lead to upper airway patency or obstruction during sleep are of obvious importance in increasing the understanding of the pathophysiology of obstructive sleep apnea in children. For most children, enlargement of the tonsils and/or adenoid is the proximate cause for the development of obstructive sleep apnea.

The static pressure and/or area relationships of the passive pharynx were endoscopically measured in 14 children with obstructive sleep apnea and in 13 healthy children under general anesthesia with complete paralysis, and it was determined that children with obstructive sleep apnea closed their airways at the level of enlarged adenoids and tonsils at low positive pressures, whereas healthy children required subatmospheric pressures to induce upper airway closure. The cross-sectional area of the narrowest segment was significantly smaller in children with obstructive sleep apnea and particularly involved the retropalatal and retroglossal segments. Thus, both congenital and acquired anatomic factors clearly play a significant role in the pathogenesis of pediatric obstructive sleep apnea.

Abnormal mechanical linkage between airway dilating muscles and airway walls

Malposition or malinsertion of specific dilating muscles is likely to have major consequences on the mechanical dilating efficiency. Therefore, even if a major weakness is not present, the mechanical disadvantage imposed by muscle shortening or by displacement of the muscle insertion on the pharyngeal wall undoubtedly results in diminished ability to stiffen the airway, thus leading to increased collapsibility or elevation of Pcrit.

Control of the upper airway size and stiffness depends on the relative and rhythmic contraction of a host of paired muscles, which include the palatal, pterygoid, tensor palatini, genioglossus, geniohyoid, and sternohyoid muscles. These muscles tend to promote a patent pharyngeal lumen and receive phasic activation in synchrony with phrenic nerve activation. Upon contraction, these muscles promote motion of the soft palate, mandible, tongue, and hyoid bone. Although the coordinated action of these muscles during the respiratory cycle has yet to be deciphered, a reasonable generalization is that inspiratory muscle output stiffens the pharynx and related structures and enlarges the lumen.

The optimal activity of these muscles depends on their anatomic arrangement; for example, airway patency is compromised during increased neck flexion by changing the points of attachment of muscles acting on the hyoid bone, such that the resulting vector of their forces may be nullified. The activity of pharyngeal muscles greatly depends on various factors within the CNS and, more particularly, on the brainstem respiratory network. Wakefulness conveys a supervisory function that ensures airway patency, and sedative agents, which compromise genioglossal muscle activity, may result in significant upper airway compromise.

Mechanoreceptor-mediated and chemoreceptor-mediated genioglossal activity is critical for maintenance of upper airway patency in healthy and micrognathic infants. Changes in genioglossal activity during transitions, from oral to nasal breathing and relative to Pcrit, suggest that genioglossus activation is critical for airway patency in micrognathic infants.

 

Muscle weakness

Little evidence suggests that intrinsic muscle weakness is a major contributor to upper airway dysfunction in conditions other than those associated with neuromuscular disorders. However, ieuromuscular disorders, upper airway obstruction is frequently observed during sleep, further reinforcing the validity of the balance-of-pressures concept.

 

Abnormal neural regulation

Abnormal respiratory control does not appear to play a significant role in upper airway obstruction during sleep in children with obstructive sleep apnea. In one study, the ventilatory response to hyperoxic hypercapnic challenge in children and adolescents with obstructive sleep apnea was similar to that measured in age-matched and sex-matched controls. Similarly, no differences were found in the ventilatory response to isocapnic hypoxia. Blunting in central chemosensitivity was reported in some children with obstructive sleep apnea undergoing surgery; however, despite such reports, central chemosensitivity during sleep in children with obstructive sleep apnea was similar to that in matched controls. However, arousal to hypercapnia was blunted, suggesting that subtle alterations in the central chemosensitive arousal network may have occurred in these children.

These subtle changes have been further substantiated by examining the ventilatory response to repeated hypercapnia, whereby reciprocal changes in respiratory frequency and tidal volume occur. In addition, children with obstructive sleep apnea demonstrate impaired arousal responses to inspiratory loads during rapid eye movement (REM) and non-REM sleep, compared to controls. Neural responses to hypoxia and hypercapnia have not been well studied in children with obstructive sleep apnea and underlying syndromes.

In addition to the aforementioned considerations, diminished laryngeal reflexes to mechanoreceptor and chemoreceptor stimulation, with reduced afferent inputs into central neural regions underlying inspiratory inputs, can be present. For example, chemoreceptor stimuli, such as increased PaCO2 or decreased PaO2, stimulate the airway, dilating muscles in a preferential mode (i.e., upper airway musculature is more stimulated than the diaphragm).

This preferential recruitment tends to correct an imbalance of forces acting on the airway and, therefore, maintains airway patency. Similarly, stimuli that result from suction pressures in the nose, pharynx, or larynx rapidly stimulate the activity of upper airway dilators. This effect is also preferential to the upper airway, causing some degree of diaphragmatic inhibition and, thus, compensating for increases in upstream resistance. The function of these upper airway receptors in children with adenotonsillar hypertrophy with and without obstructive sleep apnea is not known.

 

Etiology

Obesity and hypertrophy of tonsils and/or adenoids account for most cases of obstructive sleep apnea in children. However, any anomaly of the upper airway may produce intermittent obstructive symptoms during sleep. Facial, oral, and throat eccentricities occur iumerous congenital syndromes. Certain storage diseases, hypothyroidism, and Down syndrome result in upper airway crowding due to a relative increase in tongue mass compared to mouth size.

Neuromuscular diseases contribute to obstructive sleep apnea because of abnormal muscle tone in the pharyngeal constrictors, which are responsible for maintaining airway patency. Children with Chiari malformations are usually not weak but may develop obstructive apnea due to dysfunction of the same pharyngeal muscle groups. Individuals with obesity typically have fatty infiltration of the soft tissues of the throat, limiting airway caliber and predisposing them to obstructive apnea. Persons with sickle cell anemia have a tendency toward obstructive apnea for reasons that are still unclear.

 

Disorders associated with childhood obstructive sleep apnea include, but are not limited to, the following:

·        Adenotonsillar hypertrophy, which is the most common cause of obstructive sleep apnea in children (however, the size of the tonsils and adenoids alone does not predict the presence or severity of obstructive sleep apnea)

·        Chronic nasal obstruction, including choanal stenosis, severe septal deviation, allergic rhinitis, nasal polyps, and rare nasal and/or pharyngeal tumors

·        Down syndrome

·        Pierre Robin anomaly

·        Crouzon syndrome

·        Treacher Collins syndrome

·        Klippel-Feil syndrome

·        Beckwith-Wiedemann syndrome

·        Apert syndrome

·        Prader Willi syndrome

·        Morbid obesity

·        Marfan syndrome

·        Achondroplasia

·        Laryngomalacia

·        Mucopolysaccharidoses

·        Conditions involving neuromuscular weakness, including Duchenne muscular dystrophy, Werdnig-Hoffman disease, late-onset spinal muscular atrophy, Guillain Barré syndrome, myotonic dystrophy, and myotubular myopathy

·        Chiari malformation

·        Cerebral palsy

·        Sickle cell diseases

·        Hypothyroidism

·        Hallermann-Streiff syndrome

·        Osteopetrosis

·        Oropharyngeal papillomatosis

 

Epidemiology

Ionobese and otherwise healthy children younger than 8 years, the prevalence of obstructive sleep apnea is estimated to be 1-3%. Habitual snoring is common during childhood and affects approximately 10% of children aged 2-8 years; the frequency decreases after age 9-10 years. Obesity confers 4-fold to 5-fold added risk for sleep-disordered breathing.

In the United Kingdom, approximately 1.75-2.25% of children aged 4-5 years are thought to have obstructive sleep apnea. Unfortunately, very few epidemiologic studies of childhood obstructive sleep apnea are available.

 

Racial distribution

Obstructive sleep apnea occurs more commonly among black and Hispanic individuals than among white adults and children. In patients younger than 18 years, blacks are 3.5 times more likely to develop obstructive sleep apnea than whites.

The high frequency of obstructive sleep apnea in adult Asian populations indicates that the anthropometric characteristics of the craniofacial structures in this racial group also predispose to higher obstructive sleep apnea rates in children. The frequency of obstructive sleep apnea in Hispanic children is equal to that of white children.

 

Sex distribution

The male-to-female ratio of obstructive sleep apnea in children is approximately 1:1. At puberty, the male-to-female ratio starts to increase. In older adolescents, a male preponderance emerges that essentially reflects the typical male predominance observed in the adult population. By adulthood, symptomatic men outnumber symptomatic women by 2:1 or more.

 

Age distribution

Obstructive sleep apnea is observed in children of all ages and may develop even in infancy. Retrospective studies note that a large number of parents with children in whom obstructive sleep apnea is diagnosed recall that their child’s snoring began within the first months of life. Preterm babies are at risk for more obstructive events while supine, but some have suggested that they are still at a lower risk of death from sudden infant death syndrome. However, Moon et al, citing 3 studies, report that premature infants may be at 4 times increased risk for sudden infant death syndrome compared with term infants, with the risk increasing at lower gestational age and birthweight.

Most children with obstructive sleep apnea are aged 2-10 years (coinciding with adenotonsillar lymphatic tissue growth). Children with severe obstructive apnea are likely to present when aged 3-5 years. The mean age at diagnosis has been reported to be 14 months, plus or minus 12 months.

 

Prognosis

Major morbidities associated with childhood obstructive sleep apnea include failure to thrive, difficulty concentrating and/or developmental delay, behavioral problems, hypertension, pulmonary hypertension, and, ultimately, cor pulmonale. Some pulmonologists theorize that chronic upper airway obstruction with labored breathing may result in the development of a pectus excavatum deformation in a compliant immature chest wall. Concomitant gastroesophageal reflux is likely to be exacerbated by obstructive sleep apnea.

Children with obstructive sleep apnea syndrome, as well as children with a history of loud habitual snoring, appear to be at risk for developing deficits of executive function. According to the model by Beebe and Gozal, sleep fragmentation, intermittent hypoxemia, and hypercapnia contribute to dysfunction in the prefrontal areas of the brain. Executive functions include behavioral inhibition, regulation of affect and arousal, ability to analyze and synthesize, and memory. Executive dysfunction interferes with cognitive abilities and learning.

Obesity-related hypoventilation, commonly known as the pickwickian syndrome, occurs in some children who have obesity and obstructive sleep apnea. These individuals respond abnormally to both hypercapnic and hypoxemic stimuli to breathe; they have repetitive obstructive events with sleep and marked daytime sleepiness, daytime hypoventilation, and hypercapnia.

The incidence of cor pulmonale and death due to obstructive sleep apnea is unknown. Once pulmonary hypertension has developed, it is usually reversible if the underlying obstructive sleep apnea is effectively treated.

Children with severe obstructive sleep apnea may develop postobstructive pulmonary edema within a few hours of surgery undertaken to relieve upper airway obstruction. Furthermore, such patients are at risk for postoperative respiratory compromise, which is characterized by severe upper airway obstruction and may require endotracheal intubation or the use of noninvasive respiratory support such as continuous positive airway pressure via a nasal mask.

 

Prognosis after surgery

Surgical treatment of severe obstructive sleep apnea warrants an overnight observation, especially if the child is younger than 3 years or has concomitant cardiopulmonary disease, morbid obesity, hypotonia, or craniofacial anomalies.

The major determinants of surgical outcome include the apnea hypopnea index (AHI) and obesity at the time of diagnosis. The AHI is the total number of apneas and hypopneas that occur divided by the total duration of sleep in hours. An AHI of 1 or less is considered to be normal by pediatric standards. An AHI of 1-5 is very mildly increased, 5-10 is mildly increased, 10-20 is moderately increased, and greater than 20 is severely abnormal.

In children with enlarged tonsils and adenoids that lead to obstructive sleep apnea, an adenotonsillectomy usually results in complete cure, although no definitive studies have clearly demonstrated this issue.

The outcome of patients who require extensive surgical management obviously depends on the severity of the condition that leads to upper airway compromise. With the emergence of noninvasive ventilation as an alternative option for these children, upper airway obstruction during sleep can be conservatively and successfully managed in most children.

In children with failure to thrive (FTT), treatment of obstructive sleep apnea leads to resolution of the somatic growth disturbance. Similarly, pulmonary hypertension resolves. Although major improvements ieurobehavioral outcomes are expected, data are currently insufficient to support a complete recovery in some of the cognitive abilities affected by obstructive sleep apnea.

Tauman et al reported that only 25% of children treated for obstructive sleep apnea with adenotonsillectomy had complete postoperative normalization of symptoms.

Patient Education

Patients receiving continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea must understand that they need to use their machines every night and each time they nap.

Educate families of children and adolescents who have obesity and obstructive apnea about nutrition and weight loss.

Obesity is increasing in children; 16-33% of children and adolescents are obese. Primary care providers should provide basic weight loss information and support and readily refer patients to a pediatric weight loss program. A pediatric sleep disorders clinic should work closely with a weight loss program and can be a portal of entry for a patient into such care systems.

 

Compliance issues are of particular importance in patients treated with noninvasive ventilation. Weight loss through an appropriate program of diet and exercise is clearly beneficial for patients with obstructive sleep apnea who are obese.

 

Avoidance of certain drugs and alcohol

Patients should avoid alcohol and other depressant recreational drugs, which may worsen their sleep apnea. They should avoid sedating medications when possible; if necessary appropriate monitoring and medical supervision is required.

Infants and children with obstructive sleep apnea may have serious respiratory embarrassment when given any sedative medication. Caution is necessary during any medical or dental procedures requiring conscious sedation.

 

Respiratory insufficiency

Process of breathing consists of four stages (I – external, pulmonary respiration, II-IV — internal)

I stage. External respiration is the passage of air through the respiratory ways from the nose up to the alveoli and the process of gas exchange between the environment and the lungs. External respiration has two functions — enrichment of blood with oxygen (arterialization) and the removal of carbon dioxide,

II stage. Transport of oxygen from the lungs to the tissues.

III stage. Tissue respiration — in microcirculatory vessels oxygen is given to the tissues

IV stage. Transport of carbon dioxide from the tissues to the lungs.

Respiratory insufficiency (RI) — it is an insufficiency of the function of external respiration which leads to hypoxemia— insufficient quantity of oxygen in the arterial blood. Thus, respiratory insufficiency is a condition during which normal level of oxygen is not maintained in the blood. RI can develop in many diseases of the respiratory system (example, laryngitis, bronchitis, pneumonia, asthma, etc.) and is seen as a complication of the main disease.

 

Stages of respiratory insufficiency

 

 

As a result of hypoxemia, hypoxia develops — insufficient quantity of oxygen in the body.

 

However do not overlook other reasons of hypoxia:

·      Anemic hypoxia — insufficient quantity of hemoglobin in the blood.

·       Circulatory hypoxia — in arterial blood there is enough oxygen, but its distribution to the tissues is slowed and in insufficient quantity.

·       Tissue hypoxia — there is the required quantity of oxygen in the blood and its movement in blood is not impaired, but the tissues are not capable of using it fully (this frequently develops due to metabolism disorders).

Respiratory insufficiency is a frequent complication of respiratory diseases. Depending on the clinical signs, three stages of RI are differentiated

 

Background

Pediatric respiratory failure develops when the rate of gas exchange between the atmosphere and blood is unable to match the body’s metabolic demands. It is diagnosed when the patient’s respiratory system loses the ability to provide sufficient oxygen to the blood, and hypoxemia develops, or when the patient is unable to adequately ventilate, and hypercarbia and hypoxemia develop.

Management of acute respiratory failure begins with supporting the patient, followed by determining and treating the underlying etiology. While supporting the respiratory system and ensuring adequate gas exchange in the blood, the clinician should initiate an intervention specifically defined to correct the underlying condition.

 

Pathophysiology

Hypoxemia, defined as a decreased level of oxygen in the blood, is caused by one of the following abnormalities:

• Mismatch between alveolar ventilation (V) and pulmonary perfusion (Q)

• Intrapulmonary shunt

• Hypoventilation

• Abnormal diffusion of gases at the alveolar-capillary interface

• Reduction in inspired oxygen concentration

• Increased venous desaturation with cardiac dysfunction plus one or more of the above 5 factors

Hypoxemia is to be distinguished from hypoxia, defined as a decreased level of oxygen in the tissues. These 2 conditions may be closely related and may or may not coexist, but they are not synonymous.

 

Ventilation-perfusion mismatch, intrapulmonary shunt, and hypoventilation

The 3 most important abnormalities in gas exchange that lead to respiratory failure are V/Q mismatch, intrapulmonary shunt, and hypoventilation.

The V/Q ratio determines the adequacy of gas exchange in the lung. When alveolar ventilation matches pulmonary blood flow, CO₂ is eliminated and the blood becomes fully saturated with oxygen. In the normal lung, gravitational forces affect the V/Q ratio. When a person stands, the V/Q is greater than 1 at the apex of the lung (ventilation exceeds perfusion) and less than 1 at the base (less ventilation with more perfusion). In the overall healthy lung, the V/Q ratio is assumed to be ideal and equals 1.

A mismatch between ventilation and perfusion is the most common cause of hypoxemia. When the V/Q ratio is less than 1 throughout the lung, arterial hypoxemia results. As V/Q mismatch worsens, the minute ventilation increases producing either a low or normal arterial partial pressure of CO₂ (PaCO₂). The hypoxemia caused by low V/Q areas is responsive to supplemental oxygen administration. The more severe the V/Q imbalance, the higher the concentration of inspired oxygen is needed to raise the arterial partial pressure of oxygen (PaO₂).

In the extreme case when the V/Q ratio equals 0, pulmonary blood flow does not participate in gas exchange because the perfused lung unit receives no ventilation (V=0). This condition is intrapulmonary shunting and is calculated by comparing the oxygen contents in arterial blood, mixed venous blood, and pulmonary capillary blood (see Workup).

In healthy people, the percentage of intrapulmonary shunt is less than 10%. When the intrapulmonary shunt is greater than 30%, resultant hypoxemia does not improve with supplemental oxygenation because the shunted blood does not come in contact with the high oxygen content in the alveoli. Instead, treatment consists of recruiting and maximizing lung volume with positive pressure. PaO₂ continues to fall proportionately as the shunt increases.

In contrast, PaCO₂ remains constant because of a compensatory increase in minute ventilation until the shunt fraction exceeds 50%. The protective reflex that reduces the degree of intrapulmonary shunting is hypoxic pulmonary vasoconstriction (HPV); alveolar hypoxia leads to vasoconstriction of the perfusing vessel. This partially corrects the regional V/Q mismatch by improving PaO₂ at the expense of increasing pulmonary vascular resistance.

When ventilation is in excess of capillary blood flow, the V/Q ratio is greater than 1. At the extreme, areas of ventilated lung receive no perfusion, and the V/Q ratio approaches infinity (Q=0). This extreme condition is referred to as alveolar dead-space ventilation. In addition to alveolar dead space, anatomic dead space represents the volume of air in conducting airways that cannot participate in gas exchange.

Combined, the alveolar and anatomic dead-space volumes are referred to as physiologic dead space, which normally accounts for 30% of total ventilation. Increased dead-space ventilation results in hypoxemia and hypercapnia. This increase can be caused by decreased pulmonary perfusion due to hypotension, pulmonary embolus, or alveolar overdistention during mechanical ventilation. The ratio of dead-space to tidal-gas volume can be calculated on the basis of the difference between CO₂ in arterial blood and in exhaled gas (see Workup).

Under steady-state conditions, PaCO₂ is directly proportional to CO₂ production (VCO₂) and inversely proportional to alveolar ventilation (V_A), as follows: PaCO₂ = VCO₂ X (k/V_A), where k is a constant = 0.863.

Therefore, when V_A decreases or VCO₂ increases, PaCO₂ increases. With alveolar hypoventilation, hypoxemia is predicted by using the alveolar gas equation, but the alveolar-arterial gradient remains normal (see Workup).

Another way to approach respiratory failure is based on 2 patterns of blood-gas abnormalities. Type I respiratory failure results from poor matching of pulmonary ventilation to perfusion; this leads to noncardiac mixing of venous blood with arterial blood. As a result, type I respiratory failure is characterized by arterial hypoxemia with normal or low arterial CO₂.

Type II respiratory failure results from inadequate alveolar ventilation in relation to physiologic needs and is characterized by arterial hypercarbia and hypoxemia. Type II respiratory failure occurs when a disease or injury imposes a load on a child’s respiratory system that is greater than the power available to do the respiratory work. In this scenario, the hypoxemia is proportional to the hypercarbia.

A wide array of diseases can cause respiratory failure. Therefore, the physician must identify the affected area in the respiratory system that contributes to the respiratory failure. Identification can be achieved by dividing the respiratory system into 3 anatomic parts: (1) the extrathoracic airway, (2) the lungs responsible for gas exchange, and (3) the respiratory pump that ventilates the lung and that includes the nervous system, thorax, and respiratory muscles.

In general, diseases that affect the anatomic components of the lung result in regions of low or absent V/Q ratios, initially leading to type I (or hypoxemic) respiratory failure. In contrast, diseases of the extrathoracic airway and respiratory pump result in a respiratory power-load imbalance and type II respiratory failure. Hypercarbia due to alveolar hypoventilation is the hallmark of diseases involving the respiratory pump.

 

Pediatric considerations

The frequency of acute respiratory failure is higher in infants and young children than in adults, for several reasons. This difference can be explained by defining anatomic compartments and their developmental differences in pediatric patients that influence susceptibility to acute respiratory failure. Neonates present a unique susceptibility to respiratory failure, both resulting from and/or complicated by issues related to prematurity and transition from intrauterine to extrauterine life.

Extrathoracic airway differences

The area extending from the nose through the nasopharynx, oropharynx, and larynx to the subglottic region of the trachea constitutes the extrathoracic airway. This area differs in pediatric versus adult patients in 8 respects, as follows:

1.     Neonates and infants are obligate nasal breathers until the age of 2-6 months because of the proximity of the epiglottis to the nasopharynx. Nasal congestion can lead to clinically significant distress in this age group.

2.     The airway is small; this is one of the primary differences in infants and children younger than 8 years compared with older patients.

3.     Infants and young children have a large tongue that fills a small oropharynx.

4.     Infants and young children have a cephalic larynx. The larynx is opposite vertebrae C3-4 in children versus C6-7 in adults.

5.     The epiglottis is larger and more horizontal to the pharyngeal wall in children than in adults. The cephalic larynx and large epiglottis can make laryngoscopy challenging.

6.     Infants and young children have a narrow subglottic area. In children, the subglottic area is cone shaped, with the narrowest area at the cricoid ring. A small amount of subglottic edema can lead to clinically significant narrowing, increased airway resistance, and increased work of breathing. Adolescents and adults have a cylindrical airway that is narrowest at the glottic opening.

7.     In slightly older children, adenoidal and tonsillar lymphoid tissue is prominent and can contribute to airway obstruction.

8.     Uncorrected congenital anatomic abnormalities (eg, cleft palate, Pierre Robin sequence) or acquired abnormalities (eg, subglottic stenosis, laryngomalacia/tracheomalacia) may cause inspiratory obstruction.

 

Intrathoracic airway differences

The intrathoracic airways and lung include the conducting airways and alveoli, the interstitia, the pleura, the lung lymphatics, and the pulmonary circulation. There are 6 noteworthy differences between children and adults in this area, as follows:

1.     Infants and young children have fewer alveoli than do adults. The number dramatically increases during childhood, from approximately 20 million at birth to 300 million by 8 years of age. Therefore, infants and young children have a relatively small area for gas exchange.

2.     The alveolus is small. Alveolar size increases from 150-180 to 250-300 µm during childhood.

3.     Collateral ventilation is not fully developed; therefore, atelectasis is more common in children than in adults. During childhood, anatomic channels form to provide collateral ventilation to alveoli. These pathways are between adjacent alveoli (pores of Kohn), bronchiole and alveoli (Lambert channel), and adjacent bronchioles. This important feature allows alveoli to participate in gas exchange even in the presence of an obstructed distal airway.

4.     Smaller intrathoracic airways are more easily obstructed than larger ones. With age, the airways enlarge in diameter and length.

5.     Infants and young children have relatively little cartilaginous support of the airways. As cartilaginous support increases, dynamic compression during high expiratory flow rates is prevented.

6.     Residual alveolar damage from chronic lung disease of prematurity or bronchopulmonary dysplasia decreases pulmonary compliance.

 

Respiratory pump differences

The respiratory pump includes the nervous system with central control (ie, cerebrum, brainstem, spinal cord, peripheral nerves), respiratory muscles, and chest wall. The following 5 features mark the difference between the pediatric and adult population:

1.     The respiratory center is immature in infants and young children and leads to irregular respirations and an increased risk of apnea.

2.     The ribs are horizontally oriented. During inspiration, a decreased volume is displaced, and the capacity to increase tidal volume is limited compared with that in older individuals.

3.     The small surface area for the interaction between the diaphragm and thorax limits displacing volume in the vertical direction.

4.     The musculature is not fully developed. The slow-twitch fatigue-resistant muscle fibers in the infant are underdeveloped.

5.     The soft compliant chest wall provides little opposition to the deflating tendency of the lungs. This leads to a lower functional residual capacity in pediatric patients than in adults, a volume that approaches the pediatric alveolus critical closing volume.

 

Etiology

The most common reasons for respiratory failure in the pediatric population can be divided by anatomic compartments, as follows.

Acquired extrathoracic airway causes include the following:

• Infections (eg, retropharyngeal abscess, Ludwig angina, laryngotracheobronchitis, bacterial tracheitis, peritonsillar abscess)

• Trauma (eg, postextubation croup, thermal burns, foreign-body aspiration)

• Other (eg, hypertrophic tonsils and adenoid)

Congenital extrathoracic airway causes include the following:

• Subglottic stenosis

• Subglottic web or cyst

• Laryngomalacia

• Tracheomalacia

• Vascular ring

• Cystic hygroma

• Craniofacial anomalies

Intrathoracic airway and lung causes include the following:

• Acute respiratory distress syndrome (ARDS)

• Asthma

• Aspiration

• Bronchiolitis

• Bronchomalacia

• Left-sided valvular abnormalities

• Pulmonary contusion

• Near drowning

• Pneumonia

• Pulmonary edema

• Pulmonary embolus

• Sepsis

Respiratory pump causes include the following:

• Diaphragm eventration

• Diaphragmatic hernia

• Flail chest

• Kyphoscoliosis

• Duchenne muscular dystrophy

• Guillain-Barré syndrome

• Infant botulism

• Myasthenia gravis

• Spinal cord trauma

• Spinal muscular atrophy (SMA)

Central control causes include the following:

• CNS infection

• Drug overdose

• Sleep apnea

• Stroke

• Traumatic brain injury

 

Prognosis

The prognosis depends on the underlying etiology leading to acute respiratory failure. It can be good when the respiratory failure is an acute event that is not associated with prolonged hypoxemia (eg, in the case of a seizure or intoxication). It may be fair to poor when a new process is associated with chronic respiratory failure secondary to a neuromuscular disease or thoracic deformity or in the case of warm hypoxia exceeding 10-20 minutes. This may herald the need for long-term mechanical ventilation.

The prognosis can vary when respiratory failure is associated with a chronic disease with acute exacerbations. Acute respiratory failure remains an important cause of morbidity and mortality in children. Cardiac arrests in children frequently result from respiratory failure. In 2000, data from the National Center for Health Statistics listed respiratory illnesses as one of the top 10 causes of pediatric mortality. Respiratory failure may be the sign of an irreversible progressive disease that leads to death (eg, idiopathic pulmonary hypertension).

 

 

Respiratory distress syndrome 

 

Background

Respiratory distress syndrome, also known as hyaline membrane disease, occurs almost exclusively in premature infants. The incidence and severity of respiratory distress syndrome are related inversely to the gestational age of the newborn infant. (See Etiology and Epidemiology.)

Enormous strides have been made in understanding the pathophysiology and management of respiratory distress syndrome, leading to improvements in morbidity and mortality in infants with the condition. Advances include the following (see Treatment and Medication):

• The use of antenatal steroids to enhance pulmonary maturity

• Appropriate resuscitation facilitated by placental transfusion and immediate use of continuous positive airway pressure (CPAP) for alveolar recruitment

• Early administration of surfactant

• The use of gentler modes of ventilation, including early use of “bubble” nasal CPAP to minimize damage to the immature lungs

• Supportive therapies, such as the diagnosis and management of patent ductus arteriosus (PDA), fluid and electrolyte management, trophic feeding and nutrition, and the use of prophylactic fluconazole

These therapies have also resulted in the survival of extremely premature infants, some of who continue to be ill with complications of prematurity. (See the image below.)

 

Complications

Although reduced, the incidence and severity of complications of respiratory distress syndrome can result in clinically significant morbidities. Sequelae of respiratory distress syndrome include the following (see Prognosis, Clinical, and Workup):

• Septicemia

• Bronchopulmonary dysplasia (BPD)

• Patent ductus arteriosus (PDA)

• Pulmonary hemorrhage

• Apnea/bradycardia

• Necrotizing enterocolitis (NEC)

• Retinopathy of prematurity (ROP)

• Hypertension

• Failure to thrive

• Intraventricular hemorrhage (IVH)

• Periventricular leukomalacia (PVL) – With associated neurodevelopmental and audiovisual handicaps

Strategic goals include focusing direct attention on anticipating and minimizing these complications and preventing premature delivery whenever possible.

 

Surfactant formation and physiology

Surfactant is a complex lipoprotein (see the image below) composed of 6 phospholipids and 4 apoproteins. Surfactant recovered by alveolar wash from most mammals contains 70-80% phospholipids, 8-10% protein, and 10% neutral lipids, primarily cholesterol. Dipalmitoyl phosphatidylcholine (DPPC), or lecithin, is functionally the principle phospholipid. Phosphatidylglycerol makes up 4-15% of the phospholipids; although it is a marker for lung maturity, it is not necessary for normal lung function.

Among the 4 surfactant apoproteins identified, surfactant protein B (SP-B) and SP-C are 2 small hydrophobic proteins that make up 2-4% of the surfactant mass and are present in commercially available surfactant preparations. SP-B and SP-C work in concert to facilitate rapid adsorption and spreading of DPPC as a monolayer to lower the surface tension at the alveolar air-fluid interface in vivo during expiration, thus preventing atelectasis.

The SP-B gene is on human chromosome 2, and its primary translation product is 40 kd, which is clipped to become an 8-kd protein in the type II cells before entering lamellar bodies to be cosecreted with phospholipids. The SP-C gene is on chromosome 8; its primary translation product, 22 kd, is processed to an extremely hydrophobic 4-kd protein that is associated with lipids in lamellar bodies.

SP-A is an innate host defense, large molecular, hydrophilic (water soluble) lectin coded on human chromosome 10 that regulates lung inflammation. SP-A contributes to the biophysical properties of surfactant primarily by decreasing protein-mediated inhibition of surfactant function. It binds to multiple organisms, such as group B streptococcus, Staphylococcus aureus, influenza virus, adenovirus, herpes simplex type 1, and respiratory syncytial virus. SP-A facilitates phagocytosis of pathogens by macrophages and their clearance from the airways. Mice that lack SP-A have no tubular myelin and have normal lung function and surfactant metabolism, indicating that SP-A is not a critical regulator of surfactant metabolism. Patients with SP-A deficiency have not been described.

SP-D is also a hydrophilic protein of 43 kd that is a collectin with structural similarities to SP-A. It has a collagenlike domain and a glycosylated region that gives it its lectinlike functions. SP-D is a large multimer that is synthesized by type II alveolar cells and Clara cells in addition to other epithelial cells in the body. It also binds pathogens and facilitates their clearance. The absence of SP-D results in increased surfactant lipid pools in the airspaces and emphysema in mice. No humans with SP-D deficiency have been described.

The components of pulmonary surfactant are synthesized in the Golgi apparatus of the endoplasmic reticulum of the type II alveolar cell. (See the image below.)

Surfactant components are synthesized from precursors in the endoplasmic reticulum and transported through the Golgi apparatus by multivesicular bodies. Components are ultimately packaged in lamellar bodies, which are intracellular storage granules for surfactant before its secretion. After secretion (exocytosis) into the liquid lining of the alveolus, surfactant phospholipids are organized into a complex lattice called tubular myelin. Tubular myelin is believed to generate the phospholipid that provides material for a monolayer at the air-liquid interface in the alveolus, which lowers surface tension. Surfactant phospholipids and proteins are subsequently taken back into type II cells, in the form of small vesicles, apparently by a specific pathway that involves endosomes, and then are transported for storage into lamellar bodies for recycling. Alveolar macrophages also take up some surfactant in the liquid layer. A single transit of the phospholipid components of surfactant through the alveolar lumeormally requires a few hours. The phospholipid in the lumen is taken back into type II cell and is reused 10 times before being degraded. Surfactant proteins are synthesized in polyribosomes and extensively modified in the endoplasmic reticulum, Golgi apparatus, and multivesicular bodies. Surfactant proteins are detected in lamellar bodies or secretory vesicles closely associated with lamellar bodies before they are secreted into the alveolus.

The components are packaged in multilamellar vesicles in the cytoplasm of the type II alveolar cell. They are secreted by a process of exocytosis, the daily rate of which may exceed the weight of the cell. Once secreted, the vesicles unwind to form bipolar monolayers of phospholipid molecules that depend on the apoproteins SP-B and SP-C to properly configure in the alveolus.

The lipid molecules are enriched in dipalmitoyl acyl groups attached to a glycerol backbone that pack tightly and generate low surface tension. Tubular myelin stores surfactant and depends on SP-B. Corners of the myelin lattice appear to be glued together with the large apoprotein SP-A, which may also have an important role in phagocytosis. Surfactant proteins are expressed in the fetal lung with increasing gestational age.

Patient education

Because the risk of prematurity and respiratory distress syndrome is increased for subsequent pregnancies, counsel the parents.

Education and counseling of parents, caregivers, and families of premature infants must be undertaken as part of discharge planning. These individuals should be advised of the potential problems infants with respiratory distress syndrome may encounter during and after their nursery stay. Audiovisual aids and handouts supplement such education.

Etiology

In premature infants, respiratory distress syndrome develops because of impaired surfactant synthesis and secretion leading to atelectasis, ventilation-perfusion (V/Q) inequality, and hypoventilation with resultant hypoxemia and hypercarbia. Blood gases show respiratory and metabolic acidosis that cause pulmonary vasoconstriction, resulting in impaired endothelial and epithelial integrity with leakage of proteinaceous exudate and formation of hyaline membranes (hence the name).

The relative deficiency of surfactant decreases lung compliance (see the image below) and functional residual capacity, with increased dead space. The resulting large V/Q mismatch and right-to-left shunt may involve as much as 80% of the cardiac output.

Lungs with HMD require far more pressure than to achieve a given volume of inflation than do lungs obtained from an infant dying of a nonrespiratory cause. Arrows indicate inspiratory and expiratory limbs of the pressure-volume curves. Note the decreased lung compliance and increased critical opening and closing pressures, respectively, in the premature infant with HMD.

Hypoxia, acidosis, hypothermia, and hypotension may impair surfactant production and/or secretion. In many neonates, oxygen toxicity with barotrauma and volutrauma in their structurally immature lungs causes an influx of inflammatory cell, which exacerbates the vascular injury, leading to bronchopulmonary dysplasia (BPD). Antioxidant deficiency and free-radical injury worsen the injury.

Upon macroscopic evaluation, the lungs of affected newborns appear airless and ruddy (ie, liverlike). Therefore, the lungs require an increased critical opening pressure to inflate. Diffuse atelectasis of distal airspaces along with distension of distal airways and perilymphatic areas are observed microscopically. Progressive atelectasis, barotrauma or volutrauma, and oxygen toxicity damage endothelial and epithelial cells lining these distal airways, resulting in exudation of fibrinous matrix derived from blood.

Hyaline membranes that line the alveoli (see the image below) may form within a half hour after birth. In larger premature infants, the epithelium begins to heal at 36-72 hours after birth, and endogenous surfactant synthesis begins. The recovery phase is characterized by regeneration of alveolar cells, including type II cells, with a resultant increase in surfactant activity. The healing process is complex.

A chronic process often ensues in infants who are extremely immature and critically ill and in infants born to mothers with chorioamnionitis, resulting in BPD. In extremely premature infants, an arrest in lung development often occurs during the saccular stage, resulting in chronic lung disease termed “new” BPD.

 

Apoprotein deficiency

The hydrophobic SP-B and SP-C are essential for lung function and pulmonary homeostasis after birth. These proteins enhance the spreading, adsorption, and stability of surfactant lipids required to reduce surface tension in the alveolus. SP-B and SP-C participate in regulating intracellular and extracellular processes critical for maintaining respiratory structure and function.

SP-B deficiency is an inherited deficiency caused by a pretranslational mechanism implied by the absence of messenger ribonucleic acid (mRNA). SP-B deficiency leads to death in term or near-term neonates and clinically manifests as respiratory distress syndrome with pulmonary hypertension, or congenital alveolar proteinosis. The genetic absence of SP-B is most often caused by a 2-base pair insertion (121 ins 2) that produces a frame shift and premature terminal signal, resulting in a complete absence of SP-B.

Approximately 15% of term infants who die of a syndrome similar to respiratory distress syndrome have SP-B deficiency. The lack of SP-B causes a lack of normal lamellar bodies in type II cells, a lack of SP-C, and the appearance of incompletely processed SP-C in the airspaces. These pro SP-C forms are diagnostic of SP-B deficiency.

Analysis of lung tissue with immunologic and biologic methods reveals an absence of one of the surfactant specific proteins, SP-B, and its mRNA. In an in-vitro study, critical structure and function in the N-terminal region of pulmonary SP-B was noted. W9 is critical to optimal surface activity, whereas prolines may promote a conformation that facilitates rapid insertion of the peptide into phospholipid monolayers compressed to the highest pressures during compression-expansion cycling.

Mutations of SP-B and SP-C cause acute respiratory distress syndrome and chronic lung disease that may be related to the intracellular accumulation of injurious proteins, extracellular deficiency of bioactive surfactant peptides, or both. Mutations in the gene for SP-C are a cause of familial and sporadic interstitial lung disease and emphysema as patients age. Mutations in other genes that cause protein misfolding and misrouting may contribute to the pathogenesis of chronic interstitial lung disease.

Hydrophilic SP-A and SP-D are lectins. In vivo and in vitro studies provide compelling support for SP-A and SP-D as mediators of various immune-cell functions. Studies have showovel roles for these proteins in the clearance of apoptotic cells, direct killing of microorganisms, and initiation of parturition. None of the currently available surfactant preparations to treat respiratory distress syndrome have SP-A and SP-D.

 

ABCA3 mutations

Mutations in the adenosine triphosphate (ATP)–binding casette gene (ABCA3) iewborns result in fatal surfactant deficiency. ABCA3 is critical for proper formation of lamellar bodies and surfactant function and may also be important for lung function in other pulmonary diseases. Because it is closely related to the ABCA1 – and ABCA4 -encoded proteins that transport phospholipids in macrophages and photoreceptor cells, it may have a role in surfactant phospholipid metabolism.

The incidence of genetic abnormalities of pulmonary surfactant disorders is unknown. In a review of 300 term infants presenting as severe respiratory distress syndrome, 14% had SP-B deficiency and 14% had a deficiency of ABCA3.

 

Risk factors

The greatest risk factor for respiratory distress syndrome is prematurity, although the syndrome does not occur in all premature newborns. Other risk factors include maternal diabetes, cesarean delivery, and asphyxia.

 

Epidemiology

Occurrence in the United States

In the United States, respiratory distress syndrome has been estimated to occur in 20,000-30,000 newborn infants each year and is a complication in about 1% pregnancies. Approximately 50% of the neonates born at 26-28 weeks’ gestation develop respiratory distress syndrome, whereas less than 30% of premature neonates born at 30-31 weeks’ gestation develop the condition.

In one report, the incidence rate of respiratory distress syndrome was 42% in infants weighing 501-1500g, with 71% reported in infants weighing 501-750g, 54% reported in infants weighing 751-1000g, 36% reported in infants weighing 1001-1250g, and 22% reported in infants weighing 1251-1500g, among the 12 university hospitals participating in the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network.

International occurrence

Respiratory distress syndrome is encountered less frequently in developing countries than elsewhere, primarily because most premature infants who are small for their gestation are stressed in utero because of malnutrition or pregnancy-induced hypertension. In addition, because most deliveries in developing countries occur at home, accurate records in these regions are unavailable to determine the frequency of respiratory distress syndrome.

Race-related demographics

Respiratory distress syndrome has been reported in all races worldwide, occurring most often in white premature infants.

Prognosis

Acute complications of respiratory distress syndrome include the following:

• Alveolar rupture

• Infection

• Intracranial hemorrhage and periventricular leukomalacia

• Patent ductus arteriosus (PDA) with increasing left-to-right shunt

• Pulmonary hemorrhage

• Necrotizing enterocolitis (NEC) and/or gastrointestinal (GI) perforation

• Apnea of prematurity

Chronic complications of respiratory distress syndrome include the following:

• Bronchopulmonary dysplasia (BPD)

• Retinopathy of prematurity (ROP)

• Neurologic impairment

Alveolar rupture

Suspect an air leak (eg, pneumomediastinum, pneumopericardium, interstitial emphysema, pneumothorax) when an infant with respiratory distress syndrome suddenly deteriorates with hypotension, apnea, or bradycardia or when metabolic acidosis is persistent.

 

Infection

Infections may complicate the management of respiratory distress syndrome and may manifest in various ways, including failure to improve, sudden deterioration, or a change in white blood cell (WBC) count or thrombocytopenia. Also, invasive procedures (eg, venipuncture, catheter insertion, use of respiratory equipment) and use of postnatal steroids provide access for organisms that may invade the immunologically compromised host.

With the advent of surfactant therapy, small and ill infants are surviving, with an increased incidence of septicemia occurring in them secondary to staphylococcal epidermidis and/or candidal infection. When septicemia is suspected, obtain blood cultures from 2 sites and start appropriate antibiotics and/or antifungal therapy until culture results are obtained. Some neonatal ICUs use prophylactic fluconazole in the extremely premature infants, achieving a decrease in the incidence of candidal septicemia.

 

Intracranial hemorrhage and periventricular leukomalacia

Intraventricular hemorrhage is observed in 20-40% of premature infants, with greater frequency in infants with respiratory distress syndrome who require mechanical ventilation. Cranial ultrasonography is performed in the first week in premature neonates younger than 32 weeks’ gestation and at 36 weeks or at the time of discharge, or as indicated (eg, suspected seizures).

Use of antenatal steroids has decreased the frequency of intracranial hemorrhage in these patients with respiratory distress syndrome. Although a few studies have shown that prophylactic indomethacin therapy may decrease intraventricular hemorrhage in premature infants, its routine use is discouraged because of the risk of intestinal perforation. Hypocarbia and chorioamnionitis are associated with an increase in periventricular leukomalacia.

 

Patent ductus arteriosus with increasing left-to-right shunt

This shunt may complicate the course of respiratory distress syndrome, especially in infants weaned rapidly after surfactant therapy. Suspect patent ductus arteriosus (PDA) in any infant who deteriorates after initial improvement or who has bloody tracheal secretions.

Although helpful in the diagnosis of PDA, cardiac murmur and wide pulse pressure are not always apparent in critically ill infants. An echocardiogram enables the clinician to confirm the diagnosis. Infants requiring low fraction of inspired oxygen (FIO₂) or who are clinically stable do not require treatment, as the PDA may close spontaneously. Ductal-dependant cardiac anomalies should be excluded prior to initiating therapy. Treat PDA with ibuprofen or indomethacin, which can be repeated during the first 2 weeks if the PDA reopens.In refractory incidents of respiratory distress syndrome or in infants in whom medical therapy is contraindicated, surgically close the PDA.

 

Pulmonary hemorrhage

The occurrence of pulmonary hemorrhage increases in tiny premature infants, especially after surfactant therapy. Increase positive end-expiratory pressure (PEEP) on the ventilator and administer intratracheal epinephrine to manage pulmonary hemorrhage. In some patients, pulmonary hemorrhage may be associated with PDA; promptly treat pulmonary hemorrhage in such individuals.

In a retrospective study, intratracheal surfactant therapy was used successfully, with the rationale that blood inhibits pulmonary surfactant.

 

Necrotizing enterocolitis and/or GI perforation

Suspect NEC and/or GI perforation in any infant with abnormal abdominal findings on physical examination. Radiography of the abdomen assists in confirming their presence. Spontaneous perforation (not necessarily as part of NEC) occasionally occurs in critically ill premature infants and has been associated with the use of steroids and/or indomethacin.

 

Apnea of prematurity

Apnea of prematurity is common in immature infants, and its incidence has increased with surfactant therapy, possibly because of early extubation. Manage apnea of prematurity with methylxanthines (caffeine) and/or bubble or continuous flow nasal continuous positive airway pressure (CPAP), nasal intermittent ventilation, or with assisted ventilation in refractory incidents. Exclude septicemia, seizures, gastroesophageal reflux, and metabolic and other causes in infants with apnea of prematurity.

 

Bronchopulmonary dysplasia

BPD is a chronic lung disease defined as a requirement for oxygen at a corrected gestational age of 36 weeks. BPD is related directly to the high volume and/or pressures used for mechanical ventilation or to manage infections, inflammation, and vitamin A deficiency. BPD increases with decreasing gestational age.

Postnatal use of surfactant therapy, gentler ventilation, vitamin A, low-dose steroids, and inhaled nitric oxide may reduce the severity of BPD.

Clinical studies have demonstrated various incidences of BPD, which has been attributed to increased survival of small and ill infants with respiratory distress syndrome. BPD may also be associated with gastroesophageal reflux or sudden infant death syndrome. Hence, consider these entities in infants with unexplained apnea before discharging them from the hospital.

 

Retinopathy of prematurity

Infants with respiratory distress syndrome who have a partial pressure of oxygen (PaO₂) value of over 100mm Hg are at increased risk for ROP. Hence, closely monitor PaO₂ and maintain it at 50-70mm Hg. Although pulse oximetry is used in all premature infants, it is not helpful in preventing ROP in tiny infants because of the flat portion of the oxygen-hemoglobin dissociation curve.

An ophthalmologist examines the eyes of all premature infants at 34 weeks’ gestation and thereafter as indicated. If ROP progresses, laser therapy or cryotherapy is used to prevent retinal detachment and blindness. Closely monitor infants with ROP for refractive errors.

Intraocular bevacizumab, a monoclonal antibody targeting the vascular endothelial growth factor, has been used successfully to treat ROP. Although it is a promising therapy for ROP, further studies are needed before it can be recommended for routine use.

 

Neurologic impairment

Neurologic impairment occurs in approximately 10-70% of infants and is related to the infant’s gestational age, the extent and type of intracranial pathology, and the presence of hypoxia and infections. Hearing and visual handicaps may further compromise development in affected infants. Patients may develop a specific learning disability and aberrant behavior. Therefore, periodically follow up on these infants to detect those with neurologic impairment, and undertake appropriate interventions.

 

 

References

а) Basic

 

1. Manual of Propaedeutic Pediatrics / S.O. Nykytyuk, N.I. Balatska, N.B. Galyash, N.O. Lishchenko, O.Y. Nykytyuk – Ternopil: TSMU, 2005. – 468 pp.

2. Kapitan T. Propaedeutics of children’s diseases and nursing of the child : [Textbook for students of higher medical educational institutions] ; Fourth edition, updated and

    translated in English / T. Kapitan – Vinnitsa: The State Cartographical Factory, 2010. – 808 pp.

3. Nelson Textbook of Pediatrics /edited by Richard E. Behrman, Robert M. Kliegman; senior editor, Waldo E. Nelson – 19^th ed. – W.B.Saunders Company, 2011. – 2680 p.

 

b) Additional

1.  www.bookfinder.com/author/american-academy-of-pediatrics 

2. www.emedicine.medscape.com

3. http://www.nlm.nih.gov/medlineplus/medlineplus.html