Effects of support surface relief pressures on heel skin blood flow in persons with and without diabetes mellitus.

OBJECTIVE To investigate the effects of pressure relief magnitude on heel blood hyperemia in persons with and without diabetes mellitus. DESIGN Study participants (1 group of persons with diabetes and 1 group without diabetes) lay on a support surface for 70 minutes with 1 heel on an end cell of a support surface. Cell pressure was computer controlled to be 20 mm Hg during support and 5 or 0 mm Hg during relief. Heel skin blood perfusion was monitored by laser Doppler on the heel and foot dorsum. Heel hyperemia was determined as ratios of skin blood perfusion areas during hyperemia to preloading (AR) and peak hyperemia to mean skin blood perfusion during preload (QR). SUBJECTS 13 persons with diabetes mellitus (6 females, 7 males; age 65.2 +/- 3.0 years) and no known diabetes-related complications, and 15 persons without diabetes mellitus (7 females, 8 males; age 54.7 +/- 3.1 years) SETTING University research center. RESULTS For the nondiabetes mellitus group, hyperemia was significantly greater with complete pressure-relief compared with partial relief (P < .001). In contrast, the diabetes mellitus group showed no significantly increased response to full relief, and the hyperemia achieved during full relief, measured by AR and QR, was significantly less than with the nondiabetes mellitus group. CONCLUSIONS These results suggest that a diabetes-related reduced microvascular vasodilatory capacity is not exceeded during partial pressure relief, but is exceeded during complete pressure relief. Accordingly, differences in hyperemic response would become unmasked only when maximum hyperemia could be established during complete heel off-loading. This would suggest that a diminished hyperemia during complete off-loading, as found in the present diabetes mellitus group, may be problematic if widely present in the diabetic (or possibly older) population, under conditions in which heel loading occurs for sustained intervals.