Partitional measurement of capillary and arteriovenous anastomotic blood flow in the human finger by laser-Doppler-flowmeter

Summary

This study was made to see whether changes in blood flow through the capillaries and arteriovenous anastomoses (AVA's) of the human finger can be measured by noninvasive flowmetry. Total finger blood flow (FBF) was measured by venous occlusion plethysmography; blood flow was measured by a laser-Doppler flowmeter (ADVANCE, ALF-2100, Tokyo, Japan) using probes with optic fiber separations of 0.3 mm (LDF-0.3) and 0.7 mm (LDF-0.7). The maximum sensitivities for LDF-0.3 and LDF-0.7 were at depths of 0.8 and 1.2 mm from the tissue surface respectively. Two series of experiments were performed on separate days. In the first series the test hand was immersed in a water bath whose temperature (T_w) was 25°C at an ambient temperature (T_a) of 25°C. T_w was raised to 35°C (local hand warming), which was then followed by an increase in T_a to 35°C (whole body warming). FBF, LDF-0.3, and LDF-0.7 increased during these thermal stimulations. However, the relationship of FBF to LDF-0.3 showed two different regression lines. In contrast, the relationship of FBF to LDF-0.7 showed a single regression line. In the second series, with T_a at 35°C, the test hand was immersed in a water bath at T_w 35°C. T_w was then raised every 10 min by 2°C steps from 35 to 41°C. At T_w 39–41°C, FBF and LDF-0.7 in the test hand were significantly decreased compared with those at T_w 35°C. In contrast, LDF-0.3 increased steadily as T_w rose from 35 to 41°C. These results suggest that laser-Doppler flowmetry, using flow probes with different optic fiber separations, can measure partitional blood flow through superficial vessels, predominantly capillaries, and deeper vessels, mainly AVA's, in the human finger.