16. Respiratory System Anatomy and Physiology

Respiratory System: Anatomy and Physiology


The number of clients with chronic respiratory problems is increasing. Respiratory disorders are common and rank as the fifth leading cause of death in the United States. They can contribute to physical and lifestyle limitations. In addition, many acute health problems, medical therapies, and surgical interventions adversely affect respiratory function temporar­ily or permanently. An adequate knowledge of anatomy, phys­iology, pathophysiology, and various diagnostic tests is needed to assess the client with respiratory problems.



The two purposes of the respiratory system are to provide a source of oxygen for tissue metabolism and to remove carbon dioxide, the major waste product of metabolism. The respira­tory system also influences the following functions:

  Acid-base balance


  Sense of smell

  Fluid balance



Upper Respiratory Tract

The upper airways consist of the nose, the sinuses, the phar­ynx (throat), and the larynx ("voice box").



The nose is the organ of smell, with receptors from cranial nerve I (olfactory) located in the upper areas. This organ is a rigid structure that contains two passages separated in the middle by the septum. The upper one third of the nose is composed of bone; the lower two thirds is composed of car­tilage, which allows limited movement. The septum and interior walls of the nasal cavity are lined with mucous membranes that have a rich blood supply. The anterior nares (nostrils or external openings into the nasal cavities) are lined with skin and hair follicles, which help keep for­eign particles or organisms from entering the lungs. The posterior nares are openings from the nasal cavity into the nasopharynx.

Three bony projections (turbinates) protrude into the nasal cavities from the walls of the internal portion of the nose. Turbinates increase the total surface area for filtering, heating, and humidifying inspired air before it passes into the nasopharynx. Inspired air entering the nose is first filtered by vibrissae in the nares. Particles not filtered out in the nares are trapped in the mucous layer of the turbinates. These particles are moved by cilia (hairlike projections) to the oropharynx, where they are either swallowed or expectorated. Inspired air is humidified by contact with the mucous mem­brane and is warmed by exposure to heat from the vascular network.

The paranasal sinuses are air-filled cavities within the bones that surround the nasal passages. Lined with cili­ated epithelium, the purposes of the sinuses are to provide reso­nance during speech and to decrease the weight of the skull.




The pharynx, or throat, serves as a passageway for both the respiratory and digestive tracts and is located behind the oral and nasal cavities. It is divided into the nasopharynx, the oropharynx, and the laryngopharynx.

The nasopharynx is located behind the nose, above the soft palate. It contains the adenoids and the distal opening of the eustachian tube. The adenoids (pharyngeal tonsils) are an im­portant defense, trapping organisms that enter the nose or mouth. The eustachian tube connects the nasopharynx with the middle ear and opens during swallowing to equalize pres­sure within the middle ear.

The oropharynx is located behind the mouth, below the na­sopharynx. It extends from the soft palate to the base of the tongue and is a shared passageway for breathing and swal­lowing. The palatine tonsils (also known as faucial tonsils) are located on the lateral borders of the oropharynx. These tonsils also guard the body against invading organisms.

The laryngopharynx is located behind the larynx and ex­tends from the base of the tongue to the esophagus. The laryngopharynx is the critical dividing point where solid foods and fluids are separated from air. At this point, the pas­sageway divides into the larynx and the esophagus.




The larynx is located above the trachea, just below the phar­ynx at the base of the tongue. It is innervated by the recurrent laryngeal nerves. The larynx is composed of several cartilages. The thyroid cartilage is the largest and is com­monly referred to as the Adam's apple. The cricoid cartilage, which contains the vocal cords, lies below the thyroid carti­lage. The cricothyroid membrane is located below the level of the vocal cords and joins the thyroid and cricoid cartilages. This site is used in an emergency for access to the lower air­ways. In this procedure, called a cricothyroidotomy (or cricothyrotomy), an opening is made between the thyroid and cricoid cartilage and results in a tracheostomy. The two ary­tenoid cartilages, which attach at the posterior ends of the vo­cal cords, are used together with the thyroid cartilage in vocal cord movement.




Inside the larynx are two pairs of vocal cords: the false vo­cal cords and the true vocal cords. The opening between the true vocal cords is the glottis. The epiglottis is a leaf-shaped, elastic structure that is attached along one edge to the top of the larynx. Its hinge-like action prevents food from entering the tracheobronchial tree (aspiration) by clos­ing over the glottis during swallowing. The epiglottis opens during breathing and coughing.




Lower Respiratory Tract

The lower airways consist of the trachea; two mainstem bronchi; lobar, segmental, and subsegmental bronchi; bron­chioles; alveolar ducts; and alveoli. The tracheobronchial tree is an inverted treelike structure consisting of muscular, cartilaginous, and elastic tissues. This system of continually branching tubes, which decrease in size from the trachea to the respiratory bronchioles, allows gases to move to and from the pulmonary parenchyma. Gas exchange takes place in the pulmonary parenchyma between the alveoli and the pulmonary capillaries.



The trachea (windpipe) is located in front of (anterior to) the esophagus. It begins at the lower edge of the cricoid cartilage of the larynx and extends to the level of the fourth or fifth tho­racic vertebra. The trachea branches into the right and left mainstem bronchi at the carina.

The trachea is composed of 6 to 10 C-shaped cartilaginous rings. The open portion of the С is the back portion of the tra­chea and contains smooth muscle that is shared with the esophagus. Low pressure must be maintained in endotracheal and tracheostomy tube cuffs to avoid causing erosion of this posterior wall and to avoid creating a tracheoesophageal fis­tula (abnormal connection between the trachea and the esophagus).


The mainstem, or primary, bronchi begin at the carina. The bronchus is similar in structure to the trachea. The right bronchus is slightly wider, shorter, and more vertical than the left bronchus. Because of the more vertical line of the right bronchus, it can be accidentally intubated when an en­dotracheal tube is passed. Similarly, when a foreign object is aspirated from the throat, it most often enters the right bronchus.



The mainstem bronchi further branch into the five secondary (lobar) bronchi that enter each of the five lobes of the lung. Each lobar bronchus is surrounded by connective tissue, blood vessels, nerves, and lymphatics, and each branches into segmental and subsegmental divisions. The cartilage of these lobar bronchi is ringlike and resists collapse. The bronchi are lined with ciliated, mucus-secreting epithelium. The cilia propel mucus up and away from the lower airway to the trachea, where the mucus is either expectorated or swallowed.


The bronchioles branch from the secondary bronchi and sub­divide into smaller and smaller tubes: the terminal and respi­ratory bronchioles. These terminal and respira­tory tubes are less than 1 mm in diameter. They have no cartilage and therefore depend entirely on the elastic recoil of the lung to remain open (patent). The terminal bronchioles do not participate in gas exchange.



Alveolar ducts, which resemble a bunch of grapes, branch from the respiratory bronchioles. Alveolar sacs arise from these ducts. The alveolar sacs contain clusters of alveoli, which are the basic units of gas exchange. A pair of healthy adult lungs contains approximately 300 mil­lion alveoli, which are surrounded by pulmonary capillaries. Because these small alveoli are so numerous and share com­mon walls, the surface area for gas exchange in the lungs is extensive. In a healthy adult, this surface area is approxi­mately the size of a tennis court. Acinus is a term used to in­dicate the structural unit consisting of a respiratory bronchi­ole, an alveolar duct, and an alveolar sac.

In the walls of the alveoli, specific cells (type II pneumocytes) secrete surfactant, a fatty protein that reduces surface tension in the alveoli. Without sufficient surfactant, atelectasis (collapse of the alveoli) ultimately occurs. In atelectasis, gas exchange is reduced because the alveolar surface area is reduced.




The lungs are sponge-like, elastic, cone-shaped organs located in the pleural cavity in the thorax. The apex (top) of each lung extends above the clavicle; the base (bottom) of each lung lies just above the diaphragm (the major muscle of inspiration). The lungs are composed of millions of alveoli and their related ducts, bronchioles, and bronchi. The right lung, which is larger than the left, is divided into three lobes: upper, middle, and lower. The left lung, which is somewhat narrower than the right lung to make room for the heart, is divided into two lobes.

The hilum is the point at which the primary bronchus, pul­monary blood vessels, nerves, and lymphatics enter each lung. Innervation of the chest wall is via the phrenic (pleura) and intercostal (diaphragm, ribs, and muscles) nerves. Innervation of the bronchi is via the vagus nerve.

The pleura is a continuous smooth membrane composed of two surfaces that totally enclose the lung. The parietal pleura lines the inside of the thoracic cavity and the upper surface of the diaphragm. The visceral pleura covers the lung surfaces, including the major fissures between the lobes. These two sur­faces are lubricated by a thin fluid that is produced by the cells lining the pleura. This lubrication allows the surfaces to glide smoothly and painlessly during respirations.

Blood flow through the lungs occurs via two separate sys­tems: bronchial and pulmonary. The bronchial system carries the blood necessary to meet the metabolic demands of the lungs. The bronchial arteries, which arise from the thoracic aorta, are part of the systemic circulation and do not partici­pate in gas exchange.

The pulmonary circulation is composed of a highly vas­cular capillary network. Oxygen-depleted blood travels from the right ventricle of the heart into the pulmonary artery, which eventually branches into arterioles that form the capil­lary networks. The capillaries are enmeshed around and through the alveoli, the site of gas exchange. Freshly oxygenated blood travels from the capillaries and through the venules to the pulmonary veins and then to the left atrium. From the left atrium, oxygenated blood flows into the left ventricle, where it is pumped throughout the sys­temic circulation.



Accessory Muscles of Respiration

Breathing occurs through changes in the size of and pressure within the thoracic cavity. Contraction and relaxation of spe­cific skeletal muscles (and the diaphragm) cause changes in the size and pressure of the thoracic cavity. Accessory muscles of respiration include the scalene muscles, which elevate the first two ribs; the sternocleidomastoid muscles, which raise the sternum; and the trapezius and pectoralis muscles, which fix the shoulders. In addition, various back and abdominal mus­cles are used when the work of breathing is increased.

Respiratory Changes Associated with Aging

Many changes associ­ated with older clients result from heredity and a lifetime of exposure to environmental stimuli (e.g., cigarette smoke, bac­teria, air pollutants, and industrial fumes and irritants). Table 27-1 shows the age-related changes in the partial pressure of arterial oxygen (Pao2).


age distructions

Respiratory disease is a major cause of acute illness and chronic disability in older clients. Although respiratory func­tion normally declines with age, there is usually little diffi­culty with the demands of ordinary activity. However, the sedentary older adult often reports feeling breathless during exercise.

It is difficult to determine which respiratory changes in older adults are related to normal aging and which changes are pathologic and associated with respiratory disease or ex­posure to pollutants. In addition, age-related disorders of the neuromuscular and cardiovascular systems may cause abnor­mal respiration, even if the lungs are normal.


The respiratory system is situated in the thorax, and is responsible for gaseous exchange between the circulatory system and the outside world. Air is taken in via the upper airways (the nasal cavity, pharynx and larynx) through the lower airways (trachea, primary bronchi and bronchial tree) and into the small bronchioles and alveoli within the lung tissue. 
Move the pointer over the coloured regions of the diagram; the names will appear at the bottom of the screen)

The lungs are divided into lobes; The left lung is composed of the upper lobe, the lower lobe and the lingula (a small remnant next to the apex of the heart), the right lung is composed of the upper, the middle and the lower lobes.

Mechanics of Breathing

To take a breath in, the external intercostal muscles contract, moving the ribcage up and out. The diaphragm moves down at the same time, creating negative pressure within the thorax. The lungs are held to the thoracic wall by thepleural membranes, and so expand outwards as well. This creates negative pressure within the lungs, and so air rushes in through the upper and lower airways.

Expiration is mainly due to the natural elasticity of the lungs, which tend to collapse if they are not held against the thoracic wall. This is the mechanism behind lung collapse if there is air in the pleural space (pneumothorax).

respiratory system


Physiology of Gas Exchange

Alveolar structure

Each branch of the bronchial tree eventually sub-divides to form very narrow terminal bronchioles, which terminate in the alveoli. There are many millions of alveloi in each lung, and these are the areas responsible for gaseous exchange, presenting a massive surface area for exchange to occur over.

Each alveolus is very closely associated with a network of capillaries containing deoxygenated blood from the pulmonary artery. The capillary and alveolar walls are very thin, allowing rapid exchange of gases by passive diffusion along concentration gradients. 
CO2 moves into the alveolus as the concentration is much lower in the alveolus than in the blood, and O2 moves out of the alveolus as the continuous flow of blood through the capillaries prevents saturation of the blood with O2 and allows maximal transfer across the membrane.



In respiratory physiology, ventilation (or ventilation rate) is the rate at which gas enters or leaves the lung. It is categorized under the following definitions:




Minute ventilation

tidal volume * respiratory rate[1][2]

the total volume of gas entering the lungs per minute.

Alveolar ventilation

(tidal volume – dead space) * respiratory rate [1]

the volume of gas per unit time that reaches the alveoli, the respiratory portions of the lungs where gas exchange occurs.

Dead space ventilation

dead space * respiratory rate[3]

the volume of gas per unit time that does not reach these respiratory portions, but instead remains in the airways (trachea, bronchi, etc.).


Ventilation occurs under the control of the autonomic nervous system from parts of the brain stem, the medulla oblongata and the pons. This area of the brain forms the respiration regulatory center, a series of interconnected brain cells within the lower and middle brain stem which coordinate respiratory movements. The sections are the pneumotaxic center, the apneustic center, and the dorsal and ventral respiratory groups. This section is especially sensitive during infancy, and the neurons can be destroyed if the infant is dropped and/or shaken violently. The result can be death due to "shaken baby syndrome".[9]

The breathing rate increases with the concentration of carbon dioxide in the blood, which is detected by peripheral chemoreceptors in the aorta and carotid artery and central chemoreceptors in the medulla. Exercise also increases respiratory rate, due to the action of proprioceptors, the increase in body temperature, the release of epinephrine, and motor impulses originating from the brain.[10] In addition, it can increase due to increased inflation in the lungs, which is detected by stretch receptors.


Inhalation is initiated by the diaphragm and supported by the external intercostal muscles. Normal resting respirations are 10 to 18 breaths per minute, with a time period of 2 seconds. During vigorous inhalation (at rates exceeding 35 breaths per minute), or in approaching respiratory failure, accessory muscles of respiration are recruited for support. These consist ofsternocleidomastoid, platysma, and the scalene muscles of the neck. Pectoral muscles and latissimus dorsi are also accessory muscles.

Under normal conditions, the diaphragm is the primary driver of inhalation. When the diaphragm contracts, the ribcage expands and the contents of the abdomen are moved downward. This results in a larger thoracic volume and negative pressure (with respect to atmospheric pressure) inside the thorax. As the pressure in the chest falls, air moves into the conducting zone. Here, the air is filtered, warmed, and humidified as it flows to the lungs.

During forced inhalation, as when taking a deep breath, the external intercostal muscles and accessory muscles aid in further expanding the thoracic cavity. During inhalation the diaphragm contracts.


Exhalation is generally a passive process; however, active or forced exhalation is achieved by the abdominal and the internal intercostal muscles. During this process air is forced or exhaled out.

The lungs have a natural elasticity: as they recoil from the stretch of inhalation, air flows back out until the pressures in the chest and the atmosphere reach equilibrium.[11]

During forced exhalation, as when blowing out a candle, expiratory muscles including the abdominal muscles and internal intercostal muscles, generate abdominal and thoracic pressure, which forces air out of the lungs.

Gas exchange

The major function of the respiratory system is gas exchange between the external environment and an organism's circulatory system. In humans and other mammals, this exchange facilitatesoxygenation of the blood with a concomitant removal of carbon dioxide and other gaseous metabolic wastes from the circulation.[12] As gas exchange occurs, the acid-base balance of the body is maintained as part of homeostasis. If proper ventilation is not maintained, two opposing conditions could occur: respiratory acidosis, a life threatening condition, and respiratory alkalosis.

Upon inhalation, gas exchange occurs at the alveoli, the tiny sacs which are the basic functional component of the lungs. The alveolar walls are extremely thin (approx. 0.2 micrometres). These walls are composed of a single layer of epithelial cells (type I and type II epithelial cells) close to the pulmonary capillaries which are composed of a single layer of endothelial cells. The close proximity of these two cell types allows permeability to gases and, hence, gas exchange. This whole mechanism of gas exchange is carried by the simple phenomenon of pressure difference. When the air pressure is high inside the lungs, the air from lungs flow out. When the air pressure is low inside, then air flows into the lungs.

Immune functions

Airway epithelial cells can secrete a variety of molecules that aid in the defense of lungs. Secretory immunoglobulins (IgA), collectins (including Surfactant A and D), defensins and other peptides and proteases, reactive oxygen species, and reactive nitrogen species are all generated by airway epithelial cells. These secretions can act directly as antimicrobials to help keep the airway free of infection. Airway epithelial cells also secrete a variety of chemokines and cytokines that recruit the traditional immune cells and others to site of infections.

Most of the respiratory system is lined with mucous membranes that contain mucosal-associated lymphoid tissue, which produces white blood cells such as lymphocytes.

Metabolic and endocrine functions of the lungs

In addition to their functions in gas exchange, the lungs have a number of metabolic functions. They manufacture surfactant for local use, as noted above. They also contain a fibrinolytic system that lyses clots in the pulmonary vessels. They release a variety of substances that enter the systemic arterial blood and they remove other substances from the systemic venous blood that reach them via the pulmonary artery. Prostaglandins are removed from the circulation, but they are also synthesized in the lungs and released into the blood when lung tissue is stretched. The lungs also activate one hormone; the physiologically inactive decapeptide angiotensin I is converted to the pressor, aldosterone-stimulating octapeptide angiotensin II in the pulmonary circulation. The reaction occurs in other tissues as well, but it is particularly prominent in the lungs. Large amounts of the angiotensin-converting enzyme responsible for this activation are located on the surface of the endothelial cells of the pulmonary capillaries. The converting enzyme also inactivates bradykinin. Circulation time through the pulmonary capillaries is less than one second, yet 70% of the angiotensin I reaching the lungs is converted to angiotensin II in a single trip through the capillaries. Four other peptidases have been identified on the surface of the pulmonary endothelial cells.


The movement of gas through the larynx, pharynx and mouth allows humans to speak, or phonate. Vocalization, or singing, in birds occurs via the syrinx, an organ located at the base of the trachea. The vibration of air flowing across the larynx (vocal cords), in humans, and the syrinx, in birds, results in sound. Because of this, gas movement is extremely vital for communicationpurposes.

Temperature control

Panting in dogs, cats and some other animals provides a means of controlling body temperature. This physiological response is used as a cooling mechanism.

Coughing and sneezing

Irritation of nerves within the nasal passages or airways, can induce coughing and sneezing. These responses cause air to be expelled forcefully from the trachea or nose, respectively. In this manner, irritants caught in the mucus which lines the respiratory tract are expelled or moved to the mouth where they can be swallowed. During coughing, contraction of the smooth muscle narrows the trachea by pulling the ends of the cartilage plates together and by pushing soft tissue out into the lumen. This increases the expired airflow rate to dislodge and remove any irritant particle or mucus.

The respiratory system is the system in the human body that enables us to breathe.

The act of breathing includes: inhaling and exhaling air in the body; the absorption of oxygen from the air in order to produce energy; the discharge of carbon dioxide, which is the byproduct of the process.

The parts of the respiratory system

The respiratory system is divided into two parts:

Upper respiratory tract:

This includes the nose, mouth, and the beginning of the trachea (the section that takes air in and lets it out).

Lower respiratory tract:

This includes the trachea, the bronchi, broncheoli and the lungs (the act of breathing takes place in this part of the system).

The organs of the lower respiratory tract are located in the chest cavity. They are delineated and protected by the ribcage, the chest bone (sternum), and the muscles between the ribs and the diaphragm (that constitute a muscular partition between the chest and the abdominal cavity).

The trachea – the tube connecting the throat to the bronchi.

The bronchi – the trachea divides into two bronchi (tubes). One leads to the left lung, the other to the right lung. Inside the lungs each of the bronchi divides into smaller bronchi.

The broncheoli - the bronchi branches off into smaller tubes called broncheoli which end in the pulmonary alveolus.

Pulmonary alveoli – tiny sacs (air sacs) delineated by a single-layer membrane with blood capillaries at the other end.

The exchange of gases takes place through the membrane of the pulmonary alveolus, which always contains air: oxygen (O2) is absorbed from the air into the blood capillaries and the action of the heart circulates it through all the tissues in the body. At the same time, carbon dioxide (CO2) is transmitted from the blood capillaries into the alveoli and then expelled through the bronchi and the upper respiratory tract.

The inner surface of the lungs where the exchange of gases takes place is very large, due to the structure of the air sacs of the alveoli.

The lungs – a pair of organs found in all vertebrates.

The structure of the lungs includes the bronchial tree – air tubes branching off from the bronchi into smaller and smaller air tubes, each one ending in a pulmonary alveolus.

The act of breathing

The act of breathing has two stages – inhalation and exhalation

·         Inhalation – the intake of air into the lungs through expansion of chest volume.

·         Exhalation – the expulsion of air from the lungs through contraction of chest volume.

Inhalation and exhalation involves muscles:

1.  Rib muscles = the muscles between the ribs in the chest.

2.  Diaphragm muscle

Muscle movement – the diaphragm and rib muscles are constantly contracting and relaxing (approximately 16 times per minute), thus causing the chest cavity to increase and decrease.

During inhalation – the muscles contract:

Contraction of the diaphragm muscle – causes the diaphragm to flatten, thus enlarging the chest cavity.

Contraction of the rib muscles – causes the ribs to rise, thus increasing the chest volume.

The chest cavity expands, thus reducing air pressure and causing air to be passively drawn into the lungs. Air passes from the high pressure outside the lungs to the low pressure inside the lungs.

During exhalation – the muscles relax:

The muscles are no longer contracting, they are relaxed.

The diaphragm curves and rises, the ribs descend – and chest volume decreases.

The chest cavity contracts thus increasing air pressure and causing the air in the lungs to be expelled through the upper respiratory tract. Exhalation, too, is passive. Air passes from the high pressure in the lungs to the low pressure in the upper respiratory tract.

Inhalation and exhalation are involuntary and therefore their control requires an effort.

Changes in chest volume during inhalation and exhalation – note that it only shows the movement of the diaphragm, not that of the rib muscles.

What Do We Measure And How Do We Measure It?

The respiratory airways include the respiratory apertures (mouth and nose), the trachea and a branching system of long, flexible tubes (bronchi) that branch of to shorter and narrower tubes (broncheoli) until they end in sacs called the pulmonary alveoli.

The lungs encompass the entire system of tubes branching out from the main bronchi to the alveoli.

Measuring the functioning of the lungs is a medical tool for diagnosing problems in the respiratory system.

Measurements of lung function

2. Air volume (in liters) – lung capacity

·         Maximum lung volume is known as TLC (total lung capacity). It can be obtained by maximum strenuous inhalation.

The maximum lung volume of a healthy adult is up to 5-6 liters. In children the maximum lung volume is up to 2-3 liters, depending on age. In infants it is up to 600-1000 milliliters.

Note! Differences in lung volume can only be caused by gender, age, and height.

·         Essential air volume is the maximum volume utilized by the lungs for inhalation, also known as VC (vital capacity).

·         Residual volume (RV) is the volume of air remaining in the lungs after strenuous exhalation when the lungs feel completely empty. Residual volume prevents the broncheoli and the alveoli from sticking together. Residual volume is approximately 1.5 liters (adults).

·         The differential between total lung capacity and residual volume is the maximal volume utilized by the lungs in order to breath. It is known as vital capacity(VC). In an adult, the VC is between 3.5 and 4.5 liters.

·         Tidal Volume or VT is the volume of air displaced between normal inspiration and expiration. In a healthy adult the tidal volume is approximately 500 milliliters.

2. Rate of airflow through the respiratory airways (into and out of the lungs).This measures the effectiveness of airflow.

3. Efficiency of diffusion of oxygen from the pulmonary alveoli into the blood (not dealt with in this unit).

TLC (total lung capacity) of children

Examining lung function

The most common, accessible and efficient method of measuring lung function is by means of a spirometer. Its purpose is to diagnose obstructive diseases of the respiratory system. It produces a diagram (graphic depiction) of the volume of air expired in a given time (liter/minute)

The spirometer shows the rate at which air is expelled from the lungs. It measures the total lung capacity up to the residual volume (this test does not show the rate at which oxygen is absorbed).

If the airways are blocked the rate of the airflow of the lungs decreases. This will show on the diagram and thus indicate that there is a problem in the airways.

The most common obstruction stems from excessive phlegm, or from swelling of the inner wall of the air ways.

The most common problem of blockage of the air ways is asthma. people suffering from asthma it take longer to empty the lungs than healthy people. For example, during the first second of exhalation, only half of the vital air capacity in their lungs is expelled as opposed to 90% in healthy people. The rest is exhaled much later.

A spirometer examination takes only a few seconds. It is completely safe but there is a need for the patient to cooperate in order to obtain accurate results.

Stages of the examination:

1.  The patient is asked to inhale as deeply as possible.

2.  The patient is asked to exhale strenuously into the spirometer.

3.  The patient is asked to continue to expel air for a few seconds, despite the strong urge to breathe in.

4.  The test is repeated twice or three times.

Respiratory rate

Children in the upper classes of elementary school breathe about 20 times per minute.

Every breath causes an inhalation of approximately 7 milliliters of air volume per kilogram of body weight.

A child who weighs 30 kilos inhales approximately 210 milliliters of air volume (210X30). In other words, in the duration of a minute some 4200 milliliters of air volume enters and be expelled from the lungs.

Athletes breathe slightly deeper and slower. With every breath they inhale approximately 10 milliliters of air per kilogram. Thus an athletic child who weighs 30 kilos will only breathe 15 times in the duration space of a minute. Each inhalation will require some 300 milliliters of air volume. In the space of a minute 4500 milliliters of air volume will enter and be expelled from the his lungs. We can deduce from this that athletes ventilate their airways in a much more efficient way.

When we are under strain we breathe faster and more deeply. Since the lungs contain a reserve of air, we do not become tired because lack of air (oxygen) is causing respiratory restriction, but because of strain and tiredness in our respiratory and heart muscles.

When we are under emotional stress (before an exam, in distress, or feeling very frightened) we breathe faster, but our breathing is shallower. For example, under stress we inhale 30 times per minute but at a rate of only 4 milliliters per kilo. In other words, overall only 3600 milliliters per minute are passing through our airways, so we feel “short of breath.”

During severe asthma attacks, the breathing of asthma patients is shallower and at a higher rate. Their breathing is thus not very efficient.


Functions of Organs in Respiratory System

Respiration begins when oxygen enters into the body through the nose and the mouth. The oxygen then travels through the trachea and pharynx where the trachea divides into two bronchi. Here the bronchi are divided into bronchial tubes, in the chest cavity, so air can be directly moved into the lungs.


The nose is the primary upper respiratory organ in which air enters into and exits from the body. Cilia and mucus line the nasal cavity and traps bacteria and foreign particles that enter in through the nose. In addition, air that passes through the nasal cavity is humidified and moistened.

The nasal septum divides the nose into two narrow nasal cavities: one area is responsible for smell and the other area is responsible for respiration. Within the walls of the nasal cavity there are frontal, nasal, ethmoid, maxillary, and sphenoid bones. Cartilage helps form the shape of the nose.


Besides the nose, air can enter into the lungs through the mouth. The pharynx is a tubular structure, positioned behind the oral and nasal cavities, that allows air to pass from the mouth to the lungs. The pharynx contains three parts: The nasopharynx, which connects the upper part of the throat with the nasal cavity; the oropharynx, positioned between the top of the epiglottis and the soft palate; and the laryngopharynx, located below the epiglottis.


From the pharynx, air enters into the larynx, commonly called the voice box. The larynx is part of the upper respiratory tract that has two main functions: a passageway for air to enter into the lungs, and a source of vocalization. The larynx is made up of the hyoid bone and cartilage, which helps regulate the flow of air. The epiglottis is a flap-like cartilage structure contained in the larynx that protects the trachea against food aspiration.


The bronchi allow the passage of air to the lungs. The trachea is made of c-shaped ringed cartilage that divides into the right and left bronchus. The right main bronchus is shorter and wider than the left main bronchus. The right bronchus is subdivided into three lobar bronchi, while the left one is divided into two lobar bronchi.


The lungs are spongy, air-filled organs located on both sides of the chest cavity. The left lung is divided into a superior and inferior lobe, and the right lung is subdivided into a superior, middle, and inferior lobe. Pleura, a thin layer of tissue, line the lungs to allow the lungs to expand and contract with ease.

Respiration is the primary function of the lungs, which includes the transfer of oxygen found in the atmosphere into the blood stream and the release of carbon dioxide into the air.


The average adult has about 600 million alveoli, which are tiny grape-like sacs at the end of the respiratory tree. The exchange of oxygen and carbon dioxide gases occurs at the alveolar level. Although effort is required to inflate the alveoli (similar to blowing up a balloon), minimal effort is needed to deflate the alveoli (similar to the deflating of a balloon).


The diaphragm is a muscular structure located between the thoracic and abdominal cavity. Contraction of the diaphragm causes the chest or thorax cavity to expand, which occurs during inhalation. During exhalation, the release of the diaphragm causes the chest or thorax cavity to contract.

Oxygen saturation


Oxygen saturation is a term referring to the concentration of oxygen in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal blood oxygen levels are considered 95-100 percent. If the level is below 90 percent, it is considered low resulting in hypoxemia. Blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to respiratory or cardiac arrest. Oxygen therapy may be used to assist in raising blood oxygen levels. Oxygenation occurs when oxygen molecules (O2) enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood. Oxygenation is commonly used to refer to medical oxygen saturation.


In medicine, oxygen saturation (SO2), commonly referred to as "sats", measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen. At low partial pressures of oxygen, most hemoglobin is deoxygenated. At around 90% (the value varies according to the clinical context) oxygen saturation increases according to an oxygen-hemoglobin dissociation curve and approaches 100% at partial oxygen pressures of >10 kPa. A pulse oximeter relies on the light absorption characteristics of saturated hemoglobin to give an indication of oxygen saturation.


This balance is maintained for the most part by chemical processes in the body to sustain aerobic metabolism and life. Using the respiratory system, red blood cells, specifically the hemoglobin, gather oxygen in the lungs and distribute it to the rest of the body. The needs of the body's blood oxygen may fluctuate such as during exercise when more oxygen is required [2] or when living at higher altitudes. A blood cell is said to be "saturated" when carrying a normal amount of oxygen. Both too high and too low levels can have adverse effects on the body.


An SaO2 (arterial oxygen saturation) value below 90% causes hypoxemia (which can also be caused by anemia). Hypoxemia due to low SaO is indicated by cyanosis. Oxygen saturation can be measured in different tissues:

·         Venous oxygen saturation (SvO2) is measured to see how much oxygen the body consumes. Under clinical treatment, a SvO2 below 60% indicates that the body is in lack of oxygen, andischemic diseases occur. This measurement is often used under treatment with a heart-lung machine (extracorporeal circulation), and can give the perfusionist an idea of how much flow the patient needs to stay healthy.

·         Tissue oxygen saturation (StO2) can be measured by near infrared spectroscopy. Although the measurements are still widely discussed, they give an idea of tissue oxygenation in various conditions.

·         Peripheral capillary oxygen saturation (SpO2) is an estimation of the oxygen saturation level usually measured with a pulse oximeter device. It can be calculated with the pulse oximetryaccording to the following formula:


Blood circulation: Red = oxygenated (arteries), Blue = deoxygenated (veins)

Medical significance

Effects of decreased oxygen saturation[4]



85% and above

No evidence of impairment

65% and less

Impaired mental function on average

55% and less

Loss of consciousness on average

Healthy individuals at sea level usually exhibit oxygen saturation values between 96% and 99%. An SaO2 (arterial oxygen saturation) value below 90% causes hypoxemia (which can also be caused by anemia). Hypoxemia due to low SaO is indicated by cyanosis, but oxygen saturation does not directly reflect tissue oxygenation. The affinity of hemoglobin to oxygen may impair or enhance oxygen release at the tissue level. Oxygen is more readily released to the tissues when pH is decreased, body temperature is increased, arterial partial pressure of carbon dioxide (PaCO2) is increased, and 2,3-DPG levels (a byproduct of glucose metabolism also found in stored blood products) are increased. When the hemoglobin has greater affinity for oxygen, less is available to the tissues. Conditions such as increased pH, decreased temperature, decreased PaCO2, and decreased 2,3-DPG will increase oxygen binding to the hemoglobin and limit its release to the tissue.

Example pulse oximeter

Pulse oximetry is a method used to measure the concentration of oxygen in the blood. A small device that clips to the body (typically a finger but may be other areas), called a pulse oximeter, uses a special light to estimate the amount of oxygen in the blood. The clip attaches to a reading meter by a wire to collect the data. Oxygen levels may also be checked through an arterial blood gas test (ABG), where blood taken from an artery is analysed for oxygen level, carbon dioxide level and acidity.

Mechanism of Breathing




This is the process by which the lungs expand to take in air then contract to expel it. The cycle of respiration, which occurs about 15 times per minute, consists of three phases:

Inspiration, Expiration and Pause

Proper breathing involves all the muscles of the head, neck, thorax and abdomen, in addition to the involuntary musculature of the larynx, trachea and bronchi.
The main muscles of respiration in normal quite breathing are the intercostals muscles and diaphragm.


External intercostals muscles Actively contract
- Ribs and sternum move upwards and outwards
- Width of chest increases from side to side, from front to back and from top to bottom

Diaphragm contracts 
- Descends
- Depth of chest increases

Capacity of thorax is increased 
Pressure between pleural surfaces is reduced.
Elastic tissue of lungs is stretched.
Lungs Expand to fill thoracic cavity
Air pressure within alveoli is now less than atmospheric pressure
Air is sucked into alveoli from atmosphere



External intercostals muscles relax
- Rib and sternum move downwards and inwards
- Width of chest diminishes

Diaphragm relaxes
- Ascends
- Depth of chest diminishes

Capacity of thorax is decreased
Pressure between pleural surfaces is increased
Elastic tissue of lungs recoils
Air pressure within alveoli is now greater than atmospheric pressure

Air is forced out of alveoli to atmosphere.

Whole body Breathing





Most of us breathe in three of four different ways. These ways of breathing can be called high, low, middle or complete breathing.

1. High breathing   refers to breathing that takes place primarily in the upper part of the chest and lungs. Also called “calvicular breathing” or “collarbone breathing”, it involves movement of the ribs, collarbone and shoulders.

High breathing is naturally shallow and a large percentage of the oxygen fails to reach the alveoli and enter into gaseous exchange.

This is the least desirable form of breathing as only the upper lobes of the lungs are used which have only a small air capacity. The upper rib cage is fairly rigid and so not much expansion of the ribs can take place. 
A great deal of muscular energy is expended in pressing against the diaphragm and in keep the ribs and shoulders raised abnormally high.

High breathing is a common cause of digestive, constipation and gynaecological problems.

2. Middle breathing   is a way of breathing in which mainly the middle parts of the lungs are filled with air. 
It exhibits some of the characteristics of both high breathing, since the ribs rise and the chest expands somewhat, and low breathing, as the diaphragm moves p and down and the abdomen in and out a little. 
In this form of breathing the ribs and chest are expanded sideways. Too often it results in a shallow type of breath. It is more efficient than high breathing, but far inferior to low breathing and the complete breath.

3. Low Breathing  refers to respiration which takes place primarily in the lower part of the chest and lungs. It consists mainly of the movement of the abdomen in and out and the corresponding movement of the diaphragm. It is sometimes also called “abdominal breathing” and “diaphragmatic breathing.”
We often use low breathing when sleeping, but whenever we become physically active: walking, running or lifting, we are likely to find abdominal breathing inadequate for our needs.

This type of breath is far superior to high or middle breathing for new reasons:

More air is taken in when inhaling due to greater movement of the lungs and the fact that the lower lobes of the lungs have a larger capacity than the upper lobes.

The diaphragm acts like a second heart. Its piston-like movements expand the base of the lungs, allowing them to suck in more venous blood. The increase in the venous circulation improves the general circulation.

The abdominal organs and the solar plexus, a very important nerve centre, are massaged by and down movements of the diaphragm.

4. Whole Body Breathing   involves the entire respiratory system and not only includes the of the lungs used in high, low and middle breathing, but expands the lungs so as to take in more air than the amounts inhaled by each of these three kinds of breathing together when employed in shallow breathing.

The complete breath is not just deep breathing; it is the deepest possible breathing. Not only does raise his shoulders, collarbone and ribs, as in high breathing, and also extend his abdomen and lower his diaphragm, as in low breathing, but he does both as much is needed to expand his lungs to their fullest capacity.

This type of breathing should only be utilised when doing breathing exercises. The rest of the time it is best to use low breathing by pushing the stomach out slightly when inhaling, and then just letting the stomach fall back to its original position in the exhale.

Corrective Breathing




"To be wholly alive is to breathe deeply, to move freely, and to feel fully.  Breath is the most fundamental, tangible link to life."

Incorrect breathing manifests itself in:

Sleeping Disturbances/ Insomnia

Anxiety / Irritability / Panic Attacks

Confused thinking / Fatigue



Digestive Problems

Elevated blood pressure

Back problems, tension and headache

Immune System Dysfunction

Healthy cells need oxygen. Oxygen is essential for assimilation of nutrients and the detoxification and elimination of waste products. It is the main energy source for our brain function

Physiological Benefits include:

Relaxes the entire body and nervous system, where tensions and anxieties are held
Relaxes the heart, reducing blood pressure
Increases oxygen levels to our cells
Supports process of detoxification
Expand the working capacity of respiratory system
Enhance left and right brain interaction
Balances the level of acidity and carbon dioxide of blood

Emotional Benefits include:

Clarity of Thought
Intellectual Fulfilment
Emotional Balance
Innovative Thinking
Sharps the mind

All of these (and much more) are well documented in various western publications both within and outside of the medical community.  Many doctors are beginning to recommend breathing exercises to their patients as a means of coping with various health problems.  While the jury is still out regarding the absolute mechanism behind the effectiveness of breathing, most researchers believe that the deep relaxation of both mind and body are central to health.


Fertility Breathing




Fertility Breathing increases oxygen levels to our cells, expands the working capacity of respiratory system and supports the functioning of the endocrine system.

Working together with acupuncturists Rangana has developed a unique breathing system incorporating the acupuncture channels.

The channels used are those associated with fertility and help to bring energy and blood flow to the centre of the body. Using this method to build on the acupuncture treatments the client is able to practise at home in between sessions.

This method is particularly useful through IVF when a good pelvic blood flow is essential.  Clients also find it a useful relaxation method.

Physiological Benefits include:

Helps circulate oxygen around the body

Increases ovarian and uterine blood flow

Reduces hormonal treatment side effects

Helps embryo implantation oxygenating the placenta

Regulates the Hypothalamus Pituitary Ovarian (HPO) axis

Calms the effects of endometriosis

Emotional Benefits include:

Increases sense of control over one’s life

Enhances quality of life and health

Restructures negative thoughts and behaviour patterns

Reduces stress

Pregnancy Breathing




How does it work? 
The session/class encompass visualization, breathing exercises and relaxation, and offer a great space in which to be still and harmonious and thus learn to relax and enjoy this special time in your life.

In what stage of pregnancy I can start?  
The sessions/classes are offered to mothers-to-be of all stages in pregnancy and are designed to promote conscious relaxation and profound presence.

Visualization will teach you to mentally “see” and affect structures within your body e.g. your muscles, your cervix, your hormones. You will also be taught how to communicate with your baby within your womb.


Creates Space

Breathing opens the body, ribcage, abdomen, diaphragm, and spine.


More fluid, diaphragm acts as a lift pump from lower half of body.

Extra Oxygen

Baby placenta


60-70% of toxins released through exhalation.


Massage the abdominal organs


At the end of the exhalation the diaphragm releases the lumbar spine, lower ribs open during inhalation touching parts of the spine that needs opening and decompressing.


Concentration and focus improved, helps with emotional seesaw of pregnancy and during labour, quietens the mind.


Slow, deep and rhythmic breathing causes a reduction in the heart rate and relaxation of the muscles.


Oddsei - What are the odds of anything.