Measurement of skin blood flow: Comparison of laser-Doppler imagery and flowmetry with plethysmography

We compared measurements of skin blood flow (SkBF) by venous occlusion plethysmography with laser-Doppler Imagery (LDI), and laser-Doppler flowmetry with both integrating (LDF-int) and single (LDF-single) fiber probes in 5 healthy volunteers. Increases in SkBF were induced by raising whole-body skin temperature from 34C to 39C and thus effect heat stress for 45-60 min. Total forearm blood flow (FBF) was measured by plethysmography. SkBF was indexed by flux perfusion units measured by LDI, LDF-int, and LDF-single. We found LDI, LDF-int, and LDF-single correlated well with FBF within each study (r=0.906-0.982), but the relationships varied among subjects. The slopes for LDI vs. FBF ranged from 23.4 to 66.8; LDF-int vs. FBF from 0.151 to 0.345; and LDF-single vs. FBF from 0.167 to 0.708 mV/ml.100ml.min. Although FBF represents total blood flow to the forearm (muscle and SkBF). the close correspondence of the results from plethysmography to LDI and LDF supports the validity of the qualitative use of these methods. However, the variability in the linear relationships among the techniques complicates quantitative use.