Circulatory Effects of Acute and Chronic Hypoxia
Technical Report,01 Feb 1967,31 Dec 1972
MEDICAL COLL OF VIRGINIA RICHMOND RICHMOND United States
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The possibility that mechanisms secondary to the increased ventilation may contribute significantly to the circulatory responses to systemic hypoxia was explored in anesthetized dogs. In 14 spontaneously breathing dogs systemic hypoxia induced by breathing 7.5 oxygen in nitrogen increased cardiac output, heart rate, mean arterial blood pressure, and femoral arterial flow, and decreased systemic and hindlimb vascular resistances. In 14 dogs whose ventilation was kept constant by means of a respirator pump and intravenous decamethonium. systemic hypoxia did not change cardiac output, femoral arterial flow, or limb vascular resistance it significantly decreased heart rate and significantly increased systemic vascular resistance. In seven spontaneously breathing dogs arterial blood PCO2 was maintained at the resting level during systemic hypoxia. The increase in heart rate was significantly less pronounced but the other circulatory findings were not differentiated from those found during hypocapnic hypoxia.