A laser Doppler device with the capability to simultaneously measure skin blood flow, microvascular volume, and erythrocyte velocity was used to assess blood flow changes in 35 insulin-dependent diabetes mellitus (IDDM) subjects, mean age 33 ± 1 yr, with average duration of diabetes 14 ± 1 yr, and in a nondiabetic control group. Blood flow was determined at 35 and 44°C at several sites on the upper and the lower extremities with a temperature-regulated probe. Blood flow was highest at both temperatures on the pulps of the index finger and the first toe, regions of high density of arteriovenous anastomoses. There was significantly greater blood flow at most locations for the nondiabetic than the diabetic group at 35°C, and the differences between the two groups were substantially larger at 44°C. At 44°C, blood flow in the control group was ∼40% greater in the upper extremity and 50% greater in the lower extremity than it was in the diabetic subjects. The differences were attributed to decreases of both microvascular volume and velocity in the diabetic group. In the upper extremity, volumes in the diabetic patients were 10–15% lower and velocities 10–40% lower than in the nondiabetic subjects. In the lower extremity, volumes were 20–25% lower and velocities 40–50% lower. We conclude that laser Doppler techniques can be used to assess microvascular changes in the skin of diabetic patients. This approach may be useful to evaluate and model diabetic microangiopathy.

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