Artificial Respiration Physiology Notes

Artificial Respiration

Conditions When Artificial Respiration Is Required

Artificial respiration is required whenever there is arrest of breathing without cardiac failure.

The arrest of breathing occurs in the following conditions:

1. Accidents
2. Drowning
3. Gas poisoning
4. Electric shock
5. Anesthesia.

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The tissues of the brain, particularly the tissues of the cerebral cortex are affected by irreversible changes if oxygen supply is stopped for 5 minutes.

• So, artificial respiration (resuscitation) must be started quickly without any delay, before the development of cardiac failure.
• The purpose of artificial respiration is to ventilate the alveoli and stimulate the respiratory centers.

Methods Of Artificial Respiration

The methods of artificial respiration are of two types:

1. Manual methods
2. Mechanical methods.

Manual Methods

• Manual methods of resuscitation can be applied quickly without waiting for the availability of any mechanical aids.
• The person affected must be provided with clear air.
• The clothes around the neck and chest regions must be loosened.
• Mouth, face, and throat should be cleared of mucus, saliva, foreign particles, etc.
• The tongue must be drawn forward and, it must be prevented from falling posteriorly which may cause airway obstruction.

There are two manual methods:

1. Mouth to mouth method
2. Holger Nielson method.

Mouth to Mouth Method:

• The subject is kept in the supine position.
• The resuscitator Kneels at the side of the subject.
• By keeping the thumb on the subject’s mouth, the lower jaw is pulled downwards.
• The nostrils of the subject are closed with the thumb and index finger of the other hand.
• The resuscitator then takes a deep breath and exhales into the subject’s mouth forcefully.
• The volume of air exhaled must be twice the normal tidal volume.
• This expands the subject’s lungs.
• Then, the resuscitator removes his mouth from that of the subject.
• Now, a passive expiration occurs in the subject due to the elastic recoil of the lungs.
• The procedure is repeated at a rate of 12-14 times a minute, till normal respiration is restored.
• Mouth to mouth method is the most effective manual method because the carbon dioxide in expired air from the resuscitator can directly stimulate the respiratory centers and facilitates the onset of respiration.
• The only disadvantage is that the close contact between the mouths of resuscitator and the subject may not be acceptable for various reasons.

Holger Nielsen Method or Back Pressure Arm Lift Method: The subject is placed in the prone position with the head turned to one side.

• The hands are placed under the cheeks with flexion at the elbow joint and abduction of arms at the shoulders.
• The resuscitator kneels beside the head of the subject.
• By placing the palm of the hands over the back of the subject, the resuscitator bends forward with straight arms (without flexion at the elbow) and applies pressure on the back of the subject.
• The weight of the resuscitator and the pressure on the back of the subject compress his chest and expel air from the lungs. Later, the resuscitator leans back.
• At the same time, he draws the subject’s arm forward by holding it just above the elbow.
• This procedure causes the expansion of the thoracic cage and the flow of air into the lungs.
• The movements are repeated at the rate of 12 per minute, till the normal respiration is restored.

Mechanical Methods:

• Mechanical methods of artificial respiration become necessary when the subject needs artificial respiration for long periods.
• It is essential during respiratory failure due to paralysis of respiratory muscles or any other cause.

The mechanical methods are of two types:

1. Drinker’s method
2. Ventilation method.

1. Drinker’s Method: The machine used in this method is called an iron lung chamber or tank respirator.

• The equipment has an airtight chamber made of iron or steel.
• The subject is placed inside this chamber with the head outside the chamber.
• By means of some pumps, the pressure inside the chamber is made positive and negative alternately.
• During the negative pressure in the chamber, the subject’s thoracic cage expands and inspiration occurs.
• And, during positive pressure, the expiration occurs.
• By using the tank respirator, the patient can survive for a longer time, even up to a period of one year till the natural respiratory functions are restored.

2. Ventilation Method:

• A rubber tube is introduced into the trachea of the patient through the mouth.
• By using a pump, air or oxygen is pumped into the lungs with pressure intermittently.
• When air is pumped, inflation of lungs occurs.
• When it is stopped, expiration occurs and the cycle is repeated.

The apparatus used for ventilation is called a ventilator, which is of two types.

1. Volume ventilator
2. Pressure ventilator.

1. Volume Ventilator:

By this ventilator, a constant volume of air is pumped into the lungs of patients intermittently with minimum pressure.

2. Pressure ventilator:

• By pressure ventilator, the air is pumped into the lungs of the subject with constant high pressure.
• The ventilators are used mostly in the case of acute respiratory failure.