Hypoxia is simply a lack of oxygen at the tissue level of the body due to a decreased partial pressure of oxygen in the inspired air. Hypoxia is serious, because it may lead to death. Diseases of the blood, the heart and circulation, and the lungs may all produce some form of hypoxia. There are four types of hypoxia: (1) the hypoxic type, in which the oxygen pressure in the blood going to the tissues is too low to saturate the haemoglobin; (2) the anaemic type, in which the amount of functional haemoglobin is too small, and hence the capacity of the blood to carry oxygen is too low; (3) the stagnant type, in which the blood is or may be normal but the flow of blood to the tissues is reduced; and (4) the histotoxic type, in which the tissue cells are poisoned and are therefore unable to make proper use of oxygen. Types of Hypoxia
Hypoxic hypoxia, this is a lack of oxygen as a result of a high altitude (decreased oxygen pressure) or by conditions that prevent or interfere with the diffusion of oxygen across the alveolar membrane (asthma, pneumonia, tumors, arterial venous shunts).
In the case of anaemic hypoxia, the total amount of haemoglobin is too small to supply the body's oxygen needs, as in anaemia or after severe bleeding, or haemoglobin that is present is rendered non-functional. Examples of the latter case are carbon monoxide poisoning and metho-globinuria, in both of which the haemoglobin is so altered by toxic agents that it becomes unavailable for oxygen transport, and thus of no respiratory value. Stagnant hypoxia, in which blood flow through the capillaries is insufficient to supply the tissues, may be general or local. If general, it may result from heart disease that impairs the circulation, impairment of veinous return of blood, or trauma that induces shock. Local stagnant hypoxia may be due to any condition that reduces or prevents the circulation of the blood in any area of the body. Examples include Raynaud's...