Journal of Applied Physiology, Vol 56, Issue 5 1403-1410, Copyright © 1984 by American Physiological Society
Effect of hypoxic hypoxia on systemic vasculature
J. Malo, H. Goldberg, R. Graham, H. Unruh and C. Skoog
Effects of hypoxic hypoxia (HH) on cardiac output (CO), CO distribution,
arterial and venous pressure-flow curves, vascular compliance, vascular
time constant (tau), and resistance to venous return (RVR) were evaluated
on six dogs. The vascular bed was isolated into four compartments depending
on venous drainage: superior vena cava (SVC), splanchnic, renal and
adrenal, and the remainder of the inferior vena cava (IVC). Low arterial O2
content and PO2 produced a threefold increase in CO at the same mean
arterial pressure and a significant redistribution of CO to the SVC.
Arterial pressure-flow curves decreased their slope (i.e., flow resistance)
by a factor of two in the IVC and renal beds and by a factor of three in
the splanchnic and SVC beds. Venous pressure-flow curves for the animal
also decreased their slope significantly. HH causes a twofold increase in
venous compliance and in mean venous pressure; tau did not change, but RVR
halved. Seventy percent of the CO increase is explained by the increase in
mean venous pressure and 30% by the reduction in RVR.
