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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.



(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.



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.
References in periodicals archive ?
Cell permeability in the hypoxic group and hypoxic + YC-1 group were significantly increased compared to the normal control group (P<0.
Endothelial function in the perinatal period played a fundamental role in the autoregulation of vascular tone and a significant part in the formation of hypoxic brain damage.
Citing that levels of the cell cycle inhibitor/tumor suppressor protein p16 are reduced within hypoxic tumors, the scientists sought to provide a molecular explanation for this phenomenon.
Therefore, this study aimed to investigate the effects of hypoxic training composed of warm-up, continuous training, interval training, elastic resistance training, and cool-down on the aerobic exercise capacity, anaerobic power, muscular function, and swimming performance of 50 and 400 m in moderately trained competitive swimmers.
2 milligrams of oxygen per liter is called anoxic and samples with no oxygen are called hypoxic.
This response suggests that HIIE reflects the onset of active vasodilator activity in either normoxic or hypoxic conditions, but does so better in the hypoxia condition.
Retrospective analysis for newborn infants with hypoxic ischemic encephalopathy.
When they enter a tumour, the nanorobotic agents can detect in a wholly autonomous fashion the oxygen-depleted tumour areas, known as hypoxic zones, and deliver the drug to them.
As a result, some in the scientific community have called for many of the results in textbooks to be verified by experiments re-performed under hypoxic conditions-details like exactly what experiments and who will carry them out, however, haven't been outlined.
5) Pronounced villous hypervascularity occurs in preuterine (diffuse, Figure 1, A, or focal, Figure 1, B), and uterine (focal, Figure 1, C and D) patterns of chronic hypoxic placental injury.
Because TRPA1 has been implicated in inflammatory responses, and inflammation and tumorigenesis are stimulated by the cyclooxygenase-2 (COX-2)/prostaglandin E2 pathway in hypoxic cancer cells.

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