Orthostatic responses of regional and capillary blood flows in the toe circulation of different age groups of men

Abstract

This study investigated the effects of aging on regional and capillary blood flow responses to orthostasis in the cutaneous circulation of the toe. Three groups of male subjects: young (Y: 20–39 yr), middle-aged (M: 40–59 yr) end older (O: 60–79 yr) consented to have capillary blood cell flow (CBF) within single vessels of the nailfold portion of their large toe and total blood flow to the toe (TBF) measured first in a reclining posture with the toe at heart level (HL) then in an erect posture that placed the toe an average of 56.5 cm below the heart (BH). CBF was obtained by multiplying measurements of capillary blood cell velocity (CBV) by the cross sectional area of the vessel’s inside diameter as measured by the width of the red cell column (WRC). Measurements of TBF were obtained by strain gauge plethysmography. In the HL position there were aging differences in CBV and WRC but not in CBF. TBF also showed no aging differences in the HL position. Orthostasis elicited a net decrease in CBF and a net increase in TBF in all three subject groups. Thus, in all age groups gravity elicited a shift of flow away from the capillaries. However, in terms of magnitude the M group showed a greater percent increase in TBF and a smaller percent decrease in CBF in response to orthostasis with the latter being significantly different from both the Y and O subjects. The percent changes in CBF between the HL and BH positions for the Y, M and O groups were respectively −46%, −23% and −48%. This suggests that reductions in cutaneous capillary flow which protect the lower extremities against edema in the upright posture are attenuated in middle-aged but not older people.