Simultaneous recording of fingertip skin blood flow changes by multiprobe laser Doppler flowmetry and...

We compared the results of skin blood flow (SBF) measurements, obtained simultaneously in adjacent fingertips by laser Doppler flowmetry (LDF) and thermal clearance (TC) probes, having approximately the same spatial and temporal characteristics. Experiments were performed in nine healthy volunteers during rest at room temperature (26-28 degrees C). A time resolution equal to about a second was achieved by speeding up the response of the thermal measurement circuit by applying the computer simulation software of the MATLAB package. The comparison revealed that the frequency-corrected TC signal correlated well with the multiprobe LDF signal (median correlation coefficient = 0.90, range = 0.84 to 0.96). At the same time the individual slope values of the regression equation ranged from 0.58 to 1.61, revealing the difficulties encountered in obtaining the invariant scaling factor between the TC and LDF measurements. The relationship between the frequency-corrected TC signal and the multiprobe LDF signal was found to be linear in the range of SBF changes of about three- to fourfold. In the case of larger fluctuations in SBF, excessive acceleration at high SBF rates was noted.