Comparative circulatory responses to systemic hypoxia in man and in unanesthetized dog.

Abstract

The circulatory response to breathing IOW-O2 containing gas mixtures for 7 min. was examined in 33 experiments on 7 unanesthetized, trained dogs previously fitted with a flowmeter probe on the ascending aorta, and in 35 experiments on 26 young, normal human volunteers. In the dog, hypoxia caused tachycardia, increase in aortic blood flow, hypertension, and hypocapnia. In man, hypoxia was associated with tachycardia, increases in stroke volume and cardiac output, decreases in systemic vascular resistance and arterial blood PCO2 [CO2 tension], but with no change in mean arterial blood pressure.