an·ox·i·a
/aˈnäksēə/
noun
technical
noun: anoxia
- an absence of oxygen.
- Medicinean absence or deficiency of oxygen reaching the tissues; severe hypoxia."death due to anoxia resulting from strangulation"
Anoxia is a state of total oxygen deprivation within tissues or organs. It is an extreme form of hypoxia – a condition characterized by insufficient availability of oxygen. The damage caused by partial or complete lack of oxygen supply is known as hypoxic/anoxic injury.
Anoxia is primarily caused by a lack of blood supply to the tissue, or low oxygen content in the blood. Three physiological processes are vital in maintaining an adequate oxygen level in the blood: perfusion – blood flow to the lung; ventilation – airflow to the lung; and diffusion – the exchange of gases (oxygen/carbon dioxide) between blood and air at the lung. Dysregulation of any one of these processes can lead to severe hypoxia/anoxia injuries.
What are the types of anoxia?
There are four types of anoxia:
Anoxic anoxia
Anoxic anoxia is caused by a lack of oxygen in the air (reduced atmospheric oxygen tension), such as at high altitudes. As a result, less oxygen reaches the blood, resulting in a lack of oxygen supply to the tissues.
Anemic anoxia
Anemic anoxia is occurs when red blood cells lack the ability to carry sufficient oxygen, either due to a reduction in hemoglobin or due an alteration in the capacity of the hemoglobin to carry oxygen. It may also be the result of a deficiency in red blood cells. Health conditions frequently associated with anemic anoxia include lung disorders, chronic anemia, carbon monoxide poisoning, and acute hemorrhage.
Stagnant anoxia (also called hypoxic-ischemic injury)
Stagnant anoxia occurs when blood, although well-oxygenated, is not distributed to the tissues. Stagnant anoxia is caused by conditions such as stroke, heart attack, and cardiac arrhythmias.
Toxic anoxia
Toxid anoxia occurs when toxic substances such as carbon monoxide, cyanide, narcotics, or alcohol are present in the body, restricting the delivery of oxygen to the tissue.
What are the symptoms of anoxia?
Although anoxia can affect any tissue/organ of the body, the brain is most vulnerable. Since the brain requires a large amount of oxygen (20% of the oxygen consumed by the body is taken up by the brain alone) to function normally, the effects of anoxia are most prominent in this organ. Oxygen deprivation for 4 minutes may result in brain cell death, and permanent brain damage is likely if the oxygen supply is not restored within 5 minutes.
The signs and symptoms of anoxic brain injury depend on the duration of anoxia and the intensity of damage. The most vulnerable areas of the brain are the cerebral cortex, the hippocampus, the basal ganglia, and the cerebellum.