The Respiratory System

Every day all over the world, thousands of people die in accidents on the road, in the home, in factories, on the farm, in lakes, rivers and the sea. Many of these people suffer grave injuries, while others are hardly injured at all. Doctors tell us that the majority of these people who die, die not directly from their injuries but from suffocation because, through unconsciousness they lose the ability to breather an that many of these people could have been saved if a competent rescuer trained in resuscitation were available at the the time.

The Chain of Survival

In order to understand the basic principles involved in resuscitation, it is necessary to have some idea of what happens in the body during the process of respiration.

The airway serves as the entry point for air into the respiratory system. Air s breathed in through the outh and nose; a clear passageway allows for a free flow of air to the lungs. The rescuer is responsible for making sure that this passageway is clear of obstruction.

As air enters the mouth and nose, it passes through the pharynx, which is the throat. The pharynx then divides into two passageways: one for food – the oesophagus, and the one for air – the trachea/windpipe. A small valve called the epiglottis, protects the opening of the trachea so that food or liquid does not enter the lungs when a person swallows. The trachea also contains the larynx, which is located at the top of the trachea and contains the vocal cords. The larnyx is often referred to as the voice box.


After the air passes through the trachea, it is carried into the lungs. The trachea divides into two tubes called the bronchi (singular – bronchus). The bronchi branch out into smaller and smaller passageways, called bronchioles. These passageways end in small sacs known as alveoli. An exchange of gases takes place in the alveoli.


It is in the millions of alveoli that oxygen is transferred to the blood and exchanged for carbon dioxide that is exhaled from the body.

    1. Mouth and nose
    2. Pharynx
    3. Epiglottis
    4. Larynx
    5. Trachea
    6. Bronchi
    7. Bronchioles
    8. Alveoli

Composition of Air

Air enters the respiratory system through a process know as inhalation, and it is expelled from the system through a process known as exhalation. Inhaled air contains approximately:

  • 21% oxygen
  • 78% nitrogen
  • 0.04% carbon dioxide
  • remainder is made up of other atmospheric gases and water vapor

While exhaled air contains approximately:

  • 16% oxygen
  • 78% nitrogen
  • 4% carbon dioxide
  • remainder is made up of other atmospheric gases and water vapor


When a person breathes normally, respiration takes places automatically. There are three phases in respiration: InspirationExhalationPause:

  • Inspiration: During inhalation air is drawn into the lungs when the diaphragm contracts and its dome shape muscle flattens, this action increases the volume of the chest cavity. Atthe same time the intercostal muscles (rib muscles) cause the ribs to move up and out., further increasing the capacity of the chest cavity.
  • Exhalation: Occurs when these muscles relax. The ribs fall and the diaphragm retracts into its dome shape, forcing the air out.
  • Pause: The body rests prior to starting the inhalation phase.

The average adult breathes 12 to 20 times a minute. The body’s need for oxygen is continuous because very little oxygen an be stored in the body.


The blood goes to the heart, which pumps it through the arteries to every part of the body. The oxygen is now used up in muscular activity all over the body and the blood turns from red to a dark blue-red colour as the oxygen is replaced by carbon-dioxide (CO2). This blood, rich in CO2, travels back through the veins to the heart whence it is pumped into the lungs. In the lungs the CO2 passes from the blood vessels into the air spaces and is carried out of the body via the bronchial tubes, trachea, and mouth and nose.

Stoppage of Breathing

After an accident, the victim may stop breathing for a number of reasons:

  • The tongue may drop back and block the air passages (any accident).
  • Air may be prevented from reaching the lungs e.g. plastic bag, bed clothes or a pillow covering the mouth and nose, or a crust of bread or piece of meat stuck in the throat.
  • Some other substances may take the place of air e.g. water, carbon monoxide, gas, etc.
  • The chest wall may be immobilised by crushing e.g. in a crowd, in a house collapse.
  • The breathing system (diaphragm, pleura, etc.) may be paralysed caused by electric shock, poisoning, etc.

The victim, unless treated promptly, may die within a few minutes from lack of oxygen, which causes irreversible changes, particularly to the brain, blood and heart. Th face will have a grey/blue pallor.

Speed is essential. Seconds count. A few seconds of indecision may mean the difference between life and death for the victim. The first essential is to get the victims’ head well back and to open the mouth (head tilt, chin lift). In many cases this is sufficient to start breathing. If breathing does not begin spontaneously, rescue breathing should be started immediately.

head tilt, chin lift