Measurement of digital blood flow using the laser Doppler, impedance and strain-gauge methods

Digital volume changes and blood flow have been measured with impedance and strain-gauge plethysmography as well as with laser Doppler flowmetry. A good agreement was found between the impedance and strain-gauge flow measurements with a correlation coefficient of 0.905. The laser Doppler method recorded minor changes in finger skin blood flow following changes in posture from 30 cm below heart level to 60 cm above heart level. This result can be explained as a consequence of the limited penetration depth of laser light into the skin or as a sign of autoregulation of skin blood flow. In these experiments the total blood flow to the finger underwent major changes.