Infusion Rate Effects on Arterial Pressure,Vascular Conductance,and Muscle Weight 1

Abstract

Summary

Vascular responses to sudden changes in perfusion rate were studied by continuous simultaneous measurements of blood pressure and muscle volume in isolated, denervated gracilis muscles of dogs. The responses were also studied in a mechanical (capillaron) system (a permeable soft-walled capillary enclosed in a compliant capsule). In both systems an increase in arterial volume input was accompanied by: 1 a concordant rise in pressure, followed by 2 a transient vasodilation and fall in pressure and then by 3 a slow, progressive pressure rise. The initial pressure response to volume loading in both systems varied inversely with the compliance of the arterial system. Larger arterial compliances eliminated the first and second phases, but the tertiary phase pressure rise persisted. Thus, the initial responses, previously attributed to an active vascular response to volume loading may be due to an incidental change in perfusion pressure. The tertiary phase progressive rise in pressure in the muscle and in the capillaron system was associated with an increasing tissue volume. These results are more consistent with a decrease in vascular conductance resulting from a higher tissue pressure as the capillaron model suggests, than with an arteriolar constriction.