Effects of red cell aggregation on the venous microcirculation.

It has been shown in previous studies on perfused skeletal muscle that venous resistance and blood flow are inversely related with resistance increasing as flow falls below normal levels and decreasing during hyperemia. In one of these studies (Fig. 1) we showed that when the muscle was perfused with a non-aggregating red cell suspension of the same hematocrit as normal blood the venous resistance fell by at least 50% and the effect of flow on resistance was greatly decreased. The study cited above confirms and extends an earlier study [6] in which an inverse relation between blood flow rate and venous vascular resistance was observed. From a physiological standpoint, such a relationship is of interest because it would provide a means of automatically adjusting venous vascular resistance as blood flow changes and therefore tend to maintain capillary hydrostatic pressure constant under varying flow conditions. This is especially important in skeletal muscle where flow may readily change by a factor of five or ten in going from rest to exercise.