This document provides an overview of the human respiratory system. It describes that respiration involves the intake of oxygen and release of carbon dioxide through both external respiration in the lungs and internal respiration in tissues. The respiratory system works with the cardiovascular system to transport these gases. Key parts of the respiratory system are described including the nose, pharynx, larynx, trachea, bronchi, lungs and associated muscles and organs. Gas exchange processes like pulmonary ventilation, external respiration and internal respiration are defined. The roles and structures of the upper and lower respiratory tract are outlined.

1. Respiratory system
What is Respiration?
 Excessive CO2 produces acidity that can be toxic to cells.
 The two system that cooperate to supply O2 and eliminate CO2 are the CVS and respiratory
system.
 The respiratory system provides for gas exchange – intake of O2 and eliminate of CO2
whereas CVS transports blood containing the gases between the lungs and body parts.
 Exchange of gases (in/out) from the body is called respiration.
Two types of respiration:
 External (exchange b/w lung and blood vessels)
 Internal (exchange b/w blood and cells)
Functions of Respiratory system
 Air Distributor
 Gas exchanger
 Regulating blood pH
 Filters, warms, and humidifies air
 Produces sound
 Rids the body of some water and heat in exhaled air.
 Allows for sense of smell
Respiration Includes
 Pulmonary ventilation
◦ Air moves in and out of lungs
◦ Continuous replacement of gases in alveoli (air sacs)
 External respiration
◦ Gas exchange between blood and alveoli
◦ O2 (oxygen) in alveoli diffuses into blood
◦ CO2 (carbon dioxide) in blood diffuses into alveoli

2.  Internal respiration
◦ Gas exchange in capillaries between blood and tissue cells
◦ O2 in blood diffuses into tissues
◦ CO2 waste in tissues diffuses into blood
 Transport of respiratory gases
◦ Between the lungs and the cells of the body
◦ Performed by the cardiovascular system
◦ Blood is the transporting fluid
Cellular Respiration
 Oxygen (O2) is used by the cells
 O2 needed in conversion of glucose to cellular energy (ATP) by All body cells
 Carbon dioxide (CO2) is produced as a waste product
 The body’s cells die if either the respiratory or cardiovascular system fails
Organs of the Respiratory System
Respiratory system
 Consist of:
 Nose
 Pharynx

3.  Larynx
 Trachea
 Bronchi
 Bronchioles and smaller air passages
 Two Lungs and their coverings, the pleura
 Muscles of respiration- the intercostals muscles and the diaphragm.
On the basis of structure
Respiratory system consist two parts:
 Upper respiratory system
Contains: nose, pharynx and associated structure
 Lower respiratory system:
Contains: larynx, trachea, bronchi and lungs
Functional Anatomy of the Respiratory System
Functionally Respiratory organs have two parts
1. The conducting portion: It consists of a series of interconnecting cavities and tubes both
outside and with in lungs- Nose, Pharynx, larynx, and trachea, Bronchi, bronchioles and
terminal bronchioles – that filter, warm and moisten air and conduct it into the lungs.
The volume of the conducting portion in an adult is about 150mL.
2. The respiratory portion: It consists of tissues within the lungs were gas exchange occurs –
the respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli, the main site of gas
exchange between air and blood.
The volume of the respiratory portion in an adult is about 5 to 6 liters
The branch of medicine that deals with the diagnosis and treatment of the ears, nose and throat is
called otorhinolaryngology.
A pulmonologist is a specialist in the diagnosis and treatment of diseases of the lungs.
1. The Nose
The nose is divided in to two :
1 Internal nose – large cavity beyond nasal vestibule The main route of air entry
2. External nose – portion visible on face

4.  Divided into two equal passages by a septum
 The posterior bony part of the septum is formed by the perpendicular plate of ethmoid bone
and the vomer.
 The roof is formed by cribriform plate of the ethmoid bone and sphenoid bone, frontal bone
nasal bone.
 The floor is formed by the roof of the mouth and consists of the hard palate is composed of
the maxilla and palatine bones and the soft palate consists of involuntary muscles.
 The medial walls is formed by the septum.
 The lateral walls are formed by the maxilla, the ethmoid bone and the inferior conchae.
 The posterior wall is formed by the posterior wall of the pharynx.
 Lining of the nose:
 The nose is lined with vascular
 ciliated columnar epithelium
 Which contains mucus-secreting
 goblet cells.
Functions of nose:
 Moistens and warms air
 Filters inhaled air

5.  The projecting conchae increase the surface area and cause turbulence, spreading inspired air
over the whole nasal surface.
 Resonating chamber for speech
 Houses olfactory receptors and olfactory nerves.
The Nasal Cavity
 On the undersurface of the external nose are two openings called the External nares or
nostrils.
 The space within the internal nose is called nasal cavity.
 The anterior portion of the nasal cavity , just inside the nostrils is called vestibule and is
surrounded by cartilage.
 A verticle portion,nasal septum divides the nasal cavity into left and right sides.
 When air enters the nostrils, it passes first through the vestibule, which is lined by skin
containing coarse hairs that filter out large dust particles.
 Superior , inferior and middle nasal conchae extend out of each lateral wall of the cavity.
 The conchae almost reaching the septum , subdivided each side of the nasal cavity into a
series of groove like passage – the superior, middle and inferior Meatuses.( Meatuses –
opening).

6.  The arrangement of conchae and meatuses increases the surface area in the internal nose and
prevents dehydration.
 Two types of mucous membrane
◦ Olfactory mucosa – it lie in the membrane of the superior nasal conchae and adjacent
septum and contain olfactory (smell) receptors
◦ Respiratory mucosa - Lines nasal cavity
 Epithelium is pseudostratified ciliated columnar
 Goblet cells within epithelium
 Underlying layer of lamina propria has glands that contribute to the mucus
layer and blood vessels that warm the air.
Cilia move the mucus and trapped dust particle towards the pharynx
The Pharynx
◦ It is a funnel shaped tube about 13 cm that starts at internal nares and extends to
cricoid cartilage of larynx
◦ The pharynx lies just posterior to the nasal and oral cavities, superior to the larynx
and just anterior to the cervical vertebrae.
◦ Its wall is composed of skeletal muscle and is lined with a mucous membrane.
Functions
 Passageway for air and food
 Resonating chamber for speech sounds
 Houses tonsils which participate in immunological reactions against foreign
particle.
Divided into three sections by location
◦ Nasopharynx – superior portion,
◦ Oropharynx – continuous with the oral cavity
◦ Laryngopharynx – between the hyoid bone and the esophagus

7. The Nasopharynx
 Superior portion of the pharynx.
 It lies posterior to the nasal cavity and extends to the plane of the soft palate.
 There are five openings in its wall: two internal nares, two openings that lead into the
auditory tubes.
 And one opening in to the oropharynx.
 The posterior wall also contains the pharyngeal tonsil.
 It receives air through internal nares from the nasal cavity and receives dust mucus.
 Epithelium consists of ciliated pseudostratified epithelium that moves mucus down towards
the most inferior part of pharynx.
 It also exchange small amounts of air with the auditory tubes to equalize air pressure
between pharynx and the middle ear.
The Oropharynx
◦ It is the intermediate portion. and lies posterior to the oral cavity.
◦ Extends from soft palate to the level of the hyoid bone.

8. ◦ It has only one opening, the fauces , the opening from the mouth.
 It is line with nonkeratinized stratified squamous epithelium
 This portion has both respiratory and digestive functions because it is a common passageway
for air, food and drink.
 Two types of tonsils in the oropharynx
◦ Palatine tonsils – in the lateral walls of the pharyx
◦ Lingual tonsils – covers the posterior surface of the tongue.
The Laryngopharynx
 This is the inferior portion of pharynx.
 It begins at the level of the hyoid bone.
 It opens in to the esophagus posteriorly and the larynx anteriorly.
 Like the oropharynx it is both a respiratory and digestive pathway and is lined by
nonkeratinized startified squamous epithelium.
Structure of Pharynx
 Fibrous tissue: It is the intermediate layer. It is thicker in the nasopharynx..
 Muscle tissue: This consists of several involuntary constrictor muscles that play an important
part in the mechanism of swallowing .
 Mucous membrane lining: This lining protects underlying tissue from the abrasive action of
food stuffs passing through during swallowing.
Function of pharynx:
 Passage way of food and air: The pharynx is an organ involved in both the respiratory and
the digestive systems: air passes through the nasal and the oral parts , and food through the
oral and laryngeal parts.
 Warming and humidifying: By the same method as in nose.
 Taste: There are olfactory nerve endings of the sense of taste in the epithelium of the oral and
pharyngeal parts.
 Hearing: The auditory tube , extending from the nasal part to each middle ear, allows air to
enter the middle ear.
 Protection: The lymphatic tissue of the pharyngeal and laryngeal tonsils produces antibodies
in response to antigens.
 Speech: It act as a resonating chamber for the sound ascending from the larynx.

9. The Larynx (Voice box)
◦ Short passageway connecting laryngopharynx with trachea
◦ The wall of larynx is composed of 9 pieces of cartilage
 Three occur singly (Thyroid cartilage , epiglottis and Cricoid cartilage)
 Three occurs in pairs( Arytenoid, cuneiform and corniculate cartilage )
◦ The arytenoid cartilage are the most important because they influence the positions
and tensions of vocal folds)
Cartilages of the Larynx
Cartilages of larynx are attached to each other by ligaments and membranes.
Thyroid cartilage: This consist of two flat pieces of hyaline cartilage , or laminae , fused anteriorly
, forming laryngeal prominence ( Adam’s apple) . Immediately above the laryngeal prominence the
laminae are separated , forming a V- shaped notch known as the thyroid notch. The thyroid cartilage

10. is incomplete posteriorly and extended to form two processes called the superior and inferior cornu.
The upper part of the thyroid cartilage is lined with startified squamous epithelium like larynx and
the lower part with ciliated columnar epithelium like trachea.
Epiglottis: This is a leaf – shaped fibroelastic cartilage attached to the inner surface of the anterior
wall of the thyroid cartilage immediately below the thyroid notch. It is covered with stratified
squamous epithelium. If the larynx is likened to a box then the epiglottis acts as a lid; it closes off
the larynx during swallowing , protecting the lungs from the accidental inhalation of foreign objects.
Cricoid cartilage: It is ring of hyaline cartilage that forms the inferior wall of the larynx. It is
attached to the first ring of cartilage of the trachea by the cricotracheal ligament. The thyroid
cartilage is connected to the cricoid cartilage by the cricothyroid ligament. The cricoid cartilage is
the landmark for making an emergency airway.
Arytenoid cartilages: These are paired pyramid- shaped hyaline cartilages situated on the top of
the broad part of the cricoid forming part of the posterior wall of the larynx. They give attachment to
the vocal cords and to muscles and are lined with ciliated epithelium.
Corniculate cartilage: These are paired cartilage which are horn – shaped pieces of elastic cartilage,
are located at the apex of each arytenoid cartilage .
Cuneiform cartilages: These are club –shaped elastic cartilages anterior to the corniculate
cartilages, support the vocla folds and lateral aspects of the epiglottis.
The production of voice
 The vocal cords are two pale folds of mucous membrane with cord- like free edges which
extend from the inner wall of the thyroid prominences anteriorly to the arytenoid cartilages
posteriorly.
 When the muscle controlling the vocal cords are relaxed, the vocal cords open and the
passageway for air coming up through the larynx is clear; the vocal cords are said o be
abducted. The pitch of the sound produced by vibrating the vocal cords in this position is
low.
 When the muscles controlling the vocal cords contract, the vocal cords are stretched out
tightly across the larynx- they are said to be adducted.
 When the vocal cords are stretched to this extent, and are vibrated by air passing through
from the lungs, the sound produced is high pitched. When not in use , the vocal cords are
adducted.

11. Function of Larynx
 Production of sound: Sound has the properties of pitch, volume and resonance
◦ Pitch of the voice depends upon the length and tightness of the cords
◦ Loudness/volume depends on the force with which the cords vibrate. The greater the
force of expired air the more the cords vibrate and the louder the sound emitted.
◦ Resonance or tone is depended upon the shape of the mouth, the position of the
tongue and the lips, the facial muscles .
 Speech: This occurs during expiration when the sounds produced by the vocal cords are
manipulated by the tongue, cheeks and lips.
 Protection of lower respiratory tract: During swallowing the larynx moves upwards ,
occluding the opening into it from the pharynx and the epiglottis closes over the larynx. This
ensures that food passes into the esophagus and not in to the lower respiratory passages.

12.  Passage way of air: This is between the pharynx and trachea.
 Humidifying, filtering and warming: These continue as inspired air travels through the
larynx.
The Trachea (wind pipe)
◦ It is a tubular passageway for air that is about 12 cm long and 2.5 cm in diameter.
◦ It is located anterior to the esophagous and extends from larynx to superior border of
fifth thoracic veretbra, where it divides into right and left primary bronchi.
◦ There are 4 layers
 Mucosa
 Submucosa
 Hyaline cartilage
 Adventitia
◦ The 16-20 incomplete C-shaped rings of hyaline cartilage and are stacked one on top
of another. And open part of each C- shaped cartilage faces esophagus
 The solid C- shaped cartilage rings provide a semi rigid support so that the
tracheal wall does not collapse inward ( especially during inhalation) and
obstruct the air passageway.

13. Function of Trachea
 Support and patency: The arrangement of cartilage and elastic tissue prevents kinking and
obstruction of the airway as the head and neck move.
 Mucociliary escalator: This is the synchronous and regular beating of the cilia of the mucous
membrane lining that wafts mucus with adherent particles upwards towards the larynx where
it is swallowed or expectorated.
 Cough Reflex: Nerve endings in the larynx , trachea and bronchi are sensitive to irritation
that generates nerve impulses which are conducted by the vagus nerves to the respiratory
centre in the brain stem.
 Warming ,Humidifying and Filtering: These continue as in the nose. Although air is
normally saturated and at body temperature when it reaches the trachea.
Bronchi and Bronchioles
 At the superior border of the fifth thoracic vertebra, the trachea divides into right primary
bronchus which goes into right lung and a left primary bronchus which goes into left lung.
 At the point where the trachea divides into right and left primary bronchi is an internal ridge
called carina.
 The mucus membrane of carina is one of the most sensitive areas of the entire larynx and
trachea for triggering cough reflex.

14.  The right bronchus: This is wider , shorter and more vertical than the left bronchus and is
therefore more likely to become obstructed by an inhaled foreign body. It is about 2.5 cm
long. After entering the right lung at the hilum it divides into three branches, one to each
lobe. Each branches then subdivides into smaller branches.
 The left bronchus: This is about 5 cm long and is narrower than the right. After entering the
lung at the hilum it divides into two branches, one to each lobe. Each branches then
subdivides into smaller branches
Functions:
1. Control of air entry: The diameter of the respiratory passages is altered by contraction or
relaxation of the involuntary muscles in their walls , thus regulating the volume of air
entering the lungs. These changes are controlled by the ANS
2. The following functions continue as in the upper airways:
 Warming and humidifying

15.  Support and patency
 Removal of particulate matter
 Cough reflex
Lungs
◦ There are two lungs one lying on each side of the midline in the thoracic cavity.
◦ They are cone shaped and have an apex, a base , costal surface and medial surface.
◦ The apex: This is rounded and rises into the root of the neck , about 25 mm above the
level of the middle third of the clavicle. It lies close to the first rib and blood vessels
and nerves in the root of the neck.
◦ The base: This is concave and semilunar in shape, and lies on the thoracic surface of
the diaphragm.
◦ The costal surface: This surface is convex and lies against the costal cartilages, the
ribs and the intercoastal muscles.
◦ The medial surface: This surface is concave and has a triangular shaped area, called
the hilum, at the level of the fifth , sixth and seventh thoracic vertebra.
◦ Structure forming the root of the lung enter and leave at the hilum. These includes the
primary bronchus, the pulmonary artery supplying the lung and the two pulmonary
vein draining it.
◦ The area between the lungs is the mediastium. It is occupied by the heart, trachea,
right and left bronchi, esophagus , lymph nodes , lymph vessels and nerves.
◦ The right lung is divided into three distinct lobes : Superior , middle and inferior.
◦ The left lung smaller because the heart occupies the space left of the midline . It is
divided into two lobes : Superior and inferior.

16. The Pleura and the pleural cavity
◦ Each lung enclosed by double-layered serous membrane called pleural membrane. It
protects and encloses each lung.
◦ 1. Parietal Pleura: The superficial layer lines the wall of the thoracic cavity
◦ 2. Visceral pleura: The deep layer, covers the lungs themselves.
◦ Between the visceral and parietal pleurae is a small space , called pleural cavity,
which contains a small amount of Lubricating fluid secreted by the membranes.

17.  This fluid reduces friction between the membranes, allowing them to slide easily over one
another during breathing.
 Inflammation of the pleural membrane, called pleuritis.
 Cardiac notch – heart makes left lung 10% smaller than right.
Lobes, Fissures and lobules
 One or two fissures divide each lung into lobes.
 Both lungs have an oblique fissure, which extends inferiorly and anteriorly.
 The right lung also has a horizontal fissure.
 The oblique fissure in the left lung separates the superior lobe from the inferior lobe.
 In the right lung, the superior part of the oblique fissures separates the superior lobe from the
inferior lobe, whereas the
Inferior part of the oblique fissure separates the inferior lobe from the middle lobe.
Each lobes receives its own secondary bronchus.
Right primary bronchus give rise to three secondary bronchi called superior , middle and inferior
secondary bronchi.
 The left primary bronchus gives rise to superior and inferior secondary bronchi.

18.  Further the secondary bronchi give rise to tertiary bronchi. There are 10 tertiary bronchi in
each lung.
 The tertiary bronchi is supplied by bronchopulmonary segment and that bronchopulmonary
segment has lobules. The lobules contains terminal bronchiole which is further divide into
respiratory bronchioles and these are further divided into alveolar ducts.
Structures of the Respiratory bronchioles and alveoli
 With in each lobe, the lung tissue is further divided into lobules.
 Each lobule is supplied with air by a terminal bronchiole , which further subdivides into
respiratory bronchioles, alveolar ducts and alveoli.
 There are about 150 million alveoli in the adult lung.
 In these structures ( alveoli) the process of of air-exchanging occurs.
 Alveolar ducts and alveoli are supported by a loose network of elastic connective tissue in
which macrophages , fibroblasts, nerve and blood and lymph vessels are embedded.
 Exchange of gases in the lungs takes place across a membrane made up of alveolar wall and
capillary wall fused firmly together. This is called respiratory membrane.

19. Functions
1. External respiration
2. Defence against microbes:
3. Warming and humidifying

20. Physiology of the Respiratory System:
The major function of the respiratory system is to supply the body with oxygen and to dispose of
carbon dioxide. To do this, at least four distinct events, collectively called respiration, must occur.
Respiration:
Pulmonary ventilation: Air must move into and out of the lungs so that gasses in the air sacs are
continuously refreshed, and this process is commonly called breathing.
External respiration: Gas exchange between the pulmonary blood and alveoli must take place.
Respiratory gas transport: Oxygen and carbon dioxide must be transported to and from the
lungs and tissue cells of the body via the bloodstream.
Internal respiration: At systemic capillaries, gas exchanges must be made between the blood and
tissue cells.
Mechanism of Breathing: Volume changes lead to pressure changes, which lead to the flow of
gasses to equalize pressure.
Inspiration: Air is flowing into the lungs; chest is expanded laterally, the rib cage is elevated,
and the diaphragm is depressed and flattened; lungs are stretched to the larger thoracic volume,
causing the intrapulmonary pressure to fall and air to flow into the lungs.
Expiration: Air is leaving the lungs; the chest is depressed and the lateral dimension is reduced,
the rib cage is descended, and the diaphragm is elevated and dome-shaped; lungs recoil to a
smaller volume, intrapulmonary pressure rises, and air flows out of the lung.
Intrapulmonary volume: Intrapulmonary volume is the volume within the lungs.
Intrapleural pressure: The normal pressure within the pleural space, the intrapleural pressure, is
always negative, and this is the major factor preventing the collapse of the lungs.
Non respiratory air movements: Nonrespiratory movements are a result of reflex activity, but
some may be produced voluntarily such as cough, sneeze, crying, laughing, hiccups, and yawn.
Respiratory Volumes and Capacities:
• Tidal volume. Normal quiet breathing moves approximately 500 ml of air into and out
of the lungs with eachbreath.
• Inspiratory reserve volume. The amount of air that can be taken in forcibly over the

21. tidal volume is the inspiratory reserve volume, which is normally between 2100 ml to
3200 ml.
• Expiratory reserve volume. The amount of air that can be forcibly exhaled after a
tidal expiration, the expiratory reserve volume, is approximately 1200ml.
• Residual volume. Even after the most strenuous expiration, about 1200 ml of air still
remains in the lungs and it cannot be voluntarily expelled; this is called residual
volume, and it is important because it allows gas exchange to go on continuously even
between breaths and helps to keep the alveoli inflated.
• Vital capacity. The total amount of exchangeable air is typically around 4800 ml in
healthy young men, and this respiratory capacity is the vital capacity, which is the sum
of the tidal volume, inspiratory reserve volume, and the expiratory reserve volume.
• Dead space volume. Much of the air that enters the respiratory tract remains in the
conducting zone passageways and never reaches the alveoli; this is called the dead
space volume and during a normal tidal breath, it amounts to about 150 ml.
• Functional volume. The functional volume, which is the air that actually reaches the
respiratory zone and contributes to gas exchange, is about 350 ml.
• Spirometer: Respiratory capacities are measured with a spirometer, wherein as a person
breathes, the volumes of air exhaled can be read on an indicator, which shows the
changes in air volume inside the apparatus.
Respiratory Sounds:
Bronchial sounds: Bronchial sounds are produced by air rushing through the large respiratory
passageways (trachea and bronchi).
Vesicular breathing sounds. Vesicular breathing sounds occur as air fills the alveoli, and they
are soft and resemble a muffled breeze.
Gas transport: Oxygen is transported in the blood in two ways: most attaches to hemoglobin
molecules inside the RBCs to form oxyhemoglobin, or a very small amount of oxygen is carried
dissolved in the plasma; while carbon dioxide is transported in plasma as bicarbonate ion, or a
smaller amount (between 20 to 30 percent of the transported carbon dioxide) is carried inside the
RBCs bound to hemoglobin.

22. Control of Respiration:
Neural Regulation:
Phrenic and intercostal nerves: These two nerves regulate the activity of the respiratory muscles,
the diaphragm, and external intercostals.
Medulla and pons: Neural centers that control respiratory rhythm and depth are located mainly
in the medulla and pons; the medulla, which sets the basic rhythm of breathing, contains a
pacemaker, or self-exciting inspiratory center, and an expiratory center that inhibits the
pacemaker in a rhythmic way; pons centers appear to smooth out the basic rhythm of inspiration
and expiration set by the medulla.
Eupnea: The normal respiratory rate is referred to as eupnea, and it is maintained at a rate of 12
to 15 respirations/minute.
Hyperpnea: During exercise, we breathe more vigorously and deeply because the braincenters
send more impulses to the respiratory muscles, and this respiratory pattern are called hyperpnea.
Non-neural Factors Influencing Respiratory Rate and Depth
• Physical factors. Although the medulla’s respiratory centers set the basic rhythm of
breathing, there is no question that physical factors such as talking, coughing, and
exercising can modify the rate and depth of breathing, as well as an increased body
temperature, which increases the rate of breathing.
• Volition (conscious control). Voluntary control of breathing is limited, and the
respiratory centers will simply ignore messages from the cortex (our wishes) when the
oxygen supply in the blood is getting low or blood pH is falling.
• Emotional factors. Emotional factors also modify the rate and depth of breathing
through reflexes initiated by emotional stimuli acting through centers in the
hypothalamus.
• Chemical factors. The most important factors that modify respiratory rate and
depth are chemical- the levels of carbon dioxide and oxygen in the blood; increased
levels of carbon dioxide and decreased blood pH are the most important stimuli leading
to an increase in the rate and depth of breathing, while a decrease in oxygen levels
become important stimuli when the levels are dangerously low.
• Hyperventilation. Hyperventilation blows off more carbon dioxide and decreases the
amount of carbonic acid, which returns blood pH to normal range when carbon dioxide
or other sources of acids begin to accumulate in the blood.

23. • Hypoventilation. Hypoventilation or extremely slow or shallow breathing allows
carbon dioxide to accumulate in the blood and brings blood pH back into normal range
when blood starts to become slightly alkaline.
Artificial respiration and Resuscitation methods:
Artificial Respiration:
The first step to give artificial respiration. Artificial respiration is a lifesaving method used to
restore breathing to a person whose breathing has stopped. If breathing has stopped, the victim
will soon become unconscious. There will be no chest movement, and the skin will be pale or a
slightly bluish color. When breathing stops there is no oxygenation of the blood and irreversible
brain damage or death may occur in as little as three to six minutes. Therefore it is important to
start artificial respiration as soon as possible and continue until medical help arrives. If breathing
restarts and becomes regular, the victim should be observed continuously until medical help
arrives. The most common and efficient method of artificial respiration is mouth-to-mouth
resuscitation.
Mouth-to-Mouth Resuscitation
• Assess the responsiveness of the patient by gently shaking the victim and shouting "Are
you OK"? This precaution will prevent us from injuring during resuscitation someone
who is not truly unconscious.
• Ask someone nearby to call for Medical Help.
• Move the victim away from any dangerous location, that is, locations close to harmful
gases, fire, etc. Place the victim face up on a firm surface, such as the floor or the ground.
• Open the Airway. One very important step in the resuscitation process is to immediately
open the airway. Quite often the tongue may block the passage of air into the air passages.
To open the airway, one hand must be placed on the victim's forehead and firm, backward
pressure with the palm is applied to tilt the head back. If there is a suspicion of neck
injury, the head should not be moved unless it is absolutely necessary to open the airway.
Place the fingers of the other hand just under the chin and lift to bring the chin forward. If
there is material like vomits or any foreign body that appears to block the air passages it
must be removed.
• Ascertain whether the patient is breathing: With the airway open, look at the chest
for signs of breathing. Put your ear next to the nose and mouth and listen for breathing.
Feel for the flow of air. If there is no breathing, begin artificial respiration.

24. • Mouth-to-Mouth Resuscitation: Place one hand on the victim's forehead to pinch the
victim's nose closed. Ensure that your breathing is regular. Take a deep breath and place
your mouth tightly over the victim's mouth. If you wish you may place a thin
handkerchief between your mouth and the victim's mouth. However, do not use a very
thick cloth, as it may be difficult to blow through it. Blow until the victim's chest rises.
Listen for air being passively exhaled. Repeat with breaths at the rate of 12 times per
minute. Children should receive smaller breaths repeated at the rate of 20 times per
minute.
External Cardiac Massage:
The aim of external cardiac massage is to cause the heart to pump blood to the other parts of the
body. It should be started simultaneously with artificial respiration in a victim whose heart has
stopped beating (as made out by an absent pulse in the neck or groin). The rescuer should place
the heel of the palm of one hand parallel to and over the lower part of the victim's sternum
(breastbone), 1 to 1.5 inches from its tip. The rescuer puts the other hand on top of the first and
brings the shoulders directly over the sternum. The rescuer's fingers should not touch the victim's
chest.
Keeping the arms straight, the rescuer pushes down forcefully on the sternum. This action, called
external cardiac compression, results in blood flow from the heart to other parts of the body. The
rescuer alternately applies and releases the pressure at a rate of about 60 compressions per
minute. Each time after 15 compressions, the rescuer gives the victim artificial respiration (three
or four breaths). The ratio of 15 cardiac compressions to 3 or 4 breaths is commonly followed.
If the victim is a small child, then the rescuer must use only one hand for the cardiac
compression. For infants, the pressure is exerted using the index and middle fingers at the middle
of the sternum. In all cases, the compressions must be accompanied by artificial respiration.
Treatment should continue until medical helparrives.
Cardiopulmonary resuscitation or CPR is best performed by two trained persons. One should
administer external cardiac compression, and the other should provide artificial respiration. The
rescuers should position themselves on opposite sides of the victim so they can switch roles
easily if either becomes fatigued.