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A condition characterized by a low level of dissolved oxygen in an aquatic environment.
Oxygen deficiency; any state wherein a physiologically inadequate amount of oxygen is available to or is utilized by tissue, without respect to cause or degree. Also known as hypoxemia.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(oxygen starvation, oxygen deficiency), the lowering of the oxygen content of the tissues. The pathological condition that arises during hypoxia results from the tissues’ receiving a smaller supply of oxygen than they require (in cases of hypoxemia—lowered oxygen content of the blood). It may also arise when the tissues’ capacity to use oxygen is less than their need for oxygen. Irreversible changes take place in vital organs as a result of hypoxia. The central nervous system, heart muscle, and kidney and liver tissues are the most sensitive to oxygen deficiency.

Various hypoxic states are distinguished according to the classification adopted in 1949 at a conference on hypoxia in Kiev. Hypoxic hypoxia is a form of oxygen deficiency caused by a decrease in the oxygen content of inhaled air (for example, when climbing a mountain), by the difficulty of oxygen penetrating into the blood from the lungs because they are diseased and the air passages are obstructed, and by respiratory disturbances. Hemic hypoxia—which arises when the amount of hemoglobin capable of incorporating oxygen is reduced (decreased oxygen capacity of the blood)—develops after loss of blood, carbon monoxide poisoning, and exposure to radiation. Circulatory hypoxia occurs in cases of circulatory disorders that reduce the amount of blood flowing to the tissues per unit of time. Tissue hypoxia is a form of oxygen deficiency that is associated with changes in the activity of the respiratory enzymes. As a result of these changes the tissues are prevented from using the oxygen present in the blood that bathes them. (Tissue hypoxia develops in cases of disturbances of vitamin metabolism and in certain types of poisoning, such as cyanide.)

Hypoxia may be acute or chronic, depending on the rate at which it intensifies. In acute hypoxia, the functioning of the higher sections of the central nervous system is the first to be affected. In chronic hypoxia, the first to be affected is the functioning of the cardiovascular, respiratory, and circulatory systems. Resistance to hypoxia can be increased by training in a pressure chamber or in the mountains. Under these conditions the body develops a number of adaptive mechanisms, including reflex intensification of respiration and blood circulation, increase in the number of red blood cells as a result of their escaping from the blood depots, and increased hemoglobin content of red blood cells. These adaptations improve the individual’s sense of well-being and increase his work capacity under conditions of oxygen deficiency. It has been found that increased resistance to a given injurious factor simultaneously increases resistance to other adverse influences. For example, as the body becomes more resistant to acute hypoxia, it becomes more resistant to acceleration, ionizing radiation, heat, and great physical exertion.


Barbashova, Z. I. Akklimatizatsiia k gipoksii i ee fiziologicheskie mekhanizmy. Moscow-Leningrad, 1960.
Petrov, I. R. Kislorodnoe golodanie golovnogo mozga. [Leningrad] 1949.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A state of oxygen deficiency in the body sufficient to cause an impairment of body function. It is caused by the reduction in partial pressure of oxygen, inadequate oxygen transport, or the inability of the tissue to use oxygen. In flying, hypoxia is mostly caused by a lower partial pressure of oxygen.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
The new "Cerebral Palsy and Intrapartum Hypoxia" packet addresses causation issues, as well as nurses' failure to notify doctors of nonreassuring patterns in fetal monitor strips, failure to do a cesarean section, improperly releasing mothers from the hospital, failure to treat high-risk mothers as such, and failure to order proper tests.
Birmingham Coroner Aidan Cotter, recording a verdict of death by natural causes of intrapartum hypoxia, said there was no evidence of neglect by staff at Solihull Hospital.
With a low Sensitivity of 63.63% and a poor Specificity of 80.35%, the CTG may not be a very reliable Screening test for identifying foetuses at risk of developing intrapartum hypoxia.
Factors identified as probably avoidable in neonatal deaths in South Africa (7) Administrator related Prematurity Intrapartum hypoxia 1.
The reason for the increase in intrapartum hypoxia in HIV-exposed fetuses is not clear, but Kennedy and Fawcus hypothesise that sub-clinical chorio-amnionitis is the underlying cause.
The leading primary obstetric causes of perinatally related losses in singleton pregnancies Early Late neonatal Primary causes abortions Stillbirths deaths Infections 18 22 7 Spontaneous PTL 19 2 18 APH 11 25 4 IUGR 12 27 1 Fetal abnormality 6 13 8 Hypertensive disorders 11 4 9 Unexplained IUD 6 14 0 Intrapartum hypoxia 0 7 4 Maternal disease 3 5 1 Other 0 1 2 Birth trauma 0 3 0 Total 86 123 54 Late neonatal Primary causes deaths N (%) Infections 0 47 (17.3) Spontaneous PTL 2 41 (15.1) APH 0 40 (14.7) IUGR 0 40 (14.7) Fetal abnormality 4 31 (11.4) Hypertensive disorders 1 25 (9.2) Unexplained IUD 0 20 (7.4) Intrapartum hypoxia 1 12 (4.4) Maternal disease 0 9 (3.3) Other 1 4 (1.5) Birth trauma 0 3 (1.1) Total 9 272 Table II.