If general, it may result from heart disease that impairs the circulation, impairment of veinous return of blood, or trauma that induces shock. Stagnant hypoxia, in which blood flow through the capillaries is insufficient to supply the tissues, may be general or local. Examples of the latter case are carbon monoxide poisoning and acquired methemoglobinemia, in both of which the hemoglobin is so altered by toxic agents that it becomes unavailable for oxygen transport, and thus of no respiratory value. In the case of anemic hypoxia, either the total amount of hemoglobin is too small to supply the body’s oxygen needs, as in anemia or after severe bleeding, or hemoglobin that is present is rendered nonfunctional. The hypoxemic type of hypoxia is due to one of two mechanisms: (1) a decrease in the amount of breathable oxygen-often encountered in pilots, mountain climbers, and people living at high altitudes-due to reduced barometric pressure ( see altitude sickness) or (2) cardiopulmonary failure in which the lungs are unable to efficiently transfer oxygen from the alveoli to the blood. ![]()
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