The term hypoxia is a condition where the tissues are not oxygenated adequately, usually due to an insufficient concentration of oxygen in the blood.
The oxygen deprivation can have severe adverse effects on various body cells that need to perform important biological processes.
Some of the compensatory mechanisms adopted by the body include an increases in heart rate, myocardial contractility and cardiac output.
As the heart pumps more blood to increase the output of circulating oxygenated blood, there may be a decrease in the amount of blood supplied to the peripheral tissues, leading to a bluish discoloration or cyanosis in these areas.
This conserves oxygenated blood for the more vital organs such as the brain and the heart.
Hypoxia can be classified as local if it is affecting a specific area of the body and generalized if it involves the whole body. When there is a complete deprivation of oxygen supply in the body the term anoxia is used.
Hypoxia may be caused by various different conditions such as anaemia, in which the amount of functional hemoglobin is decreased, affecting the oxygen carrying ability of the blood.
Another example is carbon monoxide poisoning, where the chemical binds to oxygen receptors on red blood cells, effectively blocking oxygen out. Hypoxia may also be caused by conditions such as heart failure, cardiac arrest or heart attack when the circulation of blood is slowed down and therefore inadequate amounts of oxygen are supplied to the body.
Healthy people may also suffer from hypoxia. For example, if they travel to high altitudes they may develop altitude sickness which describes a lack of oxygen supplied to the bodily tissues due to a lowered partial pressure of oxygen in inhaled air.
High altitudes can also lead to the severe and even life threatening complications high altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE).
Deep sea divers are also at risk of hypoxia if their breathing gases have been incorrectly prepared or if rusty cylinders in their gas tanks have extracted oxygen.