Acute and severe hypoxia leads to unconsciousness. If not treated immediately, brain death occurs. Chronic hypoxia produces various symptoms in the body.

Effects of hypoxia are of two types:

1. Immediate effects

2. Delayed effects.

Immediate Effects

i. Effects on blood

Hypoxia induces secretion of erythropoietin from kidney. Erythropoietin increases production of RBC. This in turn, increases the oxygen carrying capacity of blood.

ii. Effects on cardiovascular system

Initially, due to the reflex stimulation of cardiac and vasomotor centers, there is an increase in rate and

force of contraction of heart, cardiac output and blood pressure. Later, there is reduction in the rate and force of contraction of heart. Cardiac output and blood pressure

are also decreased.

iii. Effects on respiration

Initially, respiratory rate increases due to chemoreceptor reflex. Because of this, large amount of carbon dioxide is washed out leading to alkalemia. Later, the respiration tends to be shallow and periodic. Finally, the rate and force of breathing are reduced to a great extent due to the failure of respiratory centers.

iv. Effects on digestive system

Hypoxia is associated with loss of appetite, nausea and vomiting. Mouth becomes dry and there is a feeling of thirst.

v. Effects on kidneys

Hypoxia causes increased secretion of erythropoietin from the juxtaglomerular apparatus. And alkaline urine is excreted.

vi. Effects on central nervous system

In mild hypoxia, the symptoms are similar to those of alcoholic intoxication.

Individual is depressed, apathetic with general loss of self control. The person becomes talkative,

quarrelsome, ill-tempered and rude. The person starts shouting, singing or crying. There is disorientation and loss of discriminative ability and loss of power of judgment. Memory is impaired. Weakness, lack of coordination and fatigue of muscles are common in hypoxia. If hypoxia is acute and severe, there is a sudden loss of consciousness. If not treated immediately, coma occurs, which leads to death.

Delayed Effects of Hypoxia

Delayed effects appear depending upon the length and severity of the exposure to hypoxia. The person becomes highly irritable and develops the symptoms of mountain sickness, such as nausea, vomiting, depression, weakness and fatigue.


Best treatment for hypoxia is oxygen therapy, i.e. treating the affected person with oxygen. Pure oxygen or oxygen combined with another gas is administered.

Oxygen therapy is carried out by two methods:

1. By placing the patient’s head in a ‘tent’ containing oxygen

2. By allowing the patient to breathe oxygen either from a mask or an intranasal tube.

Depending upon the situation, oxygen therapy can be given either under normal atmospheric pressure or

under high pressure (hyperbaric oxygen).

In Normal Atmospheric Pressure

With normal atmospheric pressure, i.e. at one atmosphere (760 mm Hg), administration of pure oxygen is

well tolerated by the patient for long hours. However, after 8 hours or more, lung tissues show fluid effusion and edema. Other tissues are not affected very much because of hemoglobin-oxygen buffer system.

In High Atmospheric Pressure – Hyperbaric Oxygen

Hyperbaric oxygen is the pure oxygen with high atmospheric pressure of 2 or more than 2 atmosphere.

Hyperbaric oxygen therapy with 2 to 3 atmosphere is tolerated by the patient for about 5 hours. During

this period, the dissolved form of oxygen increases in arterial blood because the oxygen carrying capacity

of hemoglobin is limited. At this level, tissue oxygen tension also increases to about 200 mm Hg. However, tissues tolerate the high partial pressure of oxygen, without much adverse effects. But, oxygen toxicity develops when pure oxygen is administered for long periods. Refer oxygen toxicity below.

Efficacy of Oxygen Therapy in Different Types of Hypoxia

Oxygen therapy is the best treatment for hypoxia. But it is not effective equally in all types of hypoxia. Value of oxygen therapy depends upon the type of hypoxia. So, before deciding the oxygen therapy, one should recall the physiological basis of different types of hypoxia. In hypoxic hypoxia, the oxygen therapy is 100% useful. In anemic hypoxia, oxygen therapy is moderately effective to about 70%. In stagnant hypoxia, the effectiveness of oxygen therapy is less than 50%. In histotoxic hypoxia, the oxygen therapy is not useful at all. It is because, even if oxygen is delivered, the cells cannot utilize oxygen.

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