Dickinson W. Richards Lecture: Circulatory adjustments to hypoxia.

Circulatory adjustments during hypoxia act to redistribute blood flow and maintain arterial pressure. Redistribution of blood flow is accomplished by a local effect of hypoxia, which produces dilatation in coronary and cerebral vessels, and the chemoreceptor reflex, which produces vasoconstriction in skeletal muscle and the splanchnic bed and dilatation in coronary vessels. Arterial pressure is maintained primarily by the chemoreceptor reflex. If the chemoreceptor reflex fails to maintain arterial pressure, hypoxia and hypotension together activate the central pressor response. Compensatory mechanisms usually are sufficient to maintain homeostasis during hypoxia. However, when a hypotensive stress is superimposed during hypoxia, compensatory mechanisms may fail to maintain arterial pressure. Thus, systemic hypoxia interferes with autonomic cardiovascular adjustments.