Beat-by-beat double-normalized pulse volume derived photoplethysmographically as a new quantitative index of finger vascular tone in humans

Near-infrared finger photoplethysmograms were recorded and double-normalize d pulse volumes (DNPV = Delta V-b/V-b; V-b = total blood volume in the fing ertip, Delta V-b = pulsatile component of V-b) were calculated in ten subje cts during, immersion of the contralateral band in water at three different temperatures (44 degrees C, 22 degrees C, 11 degrees C). The DNPV from the left linger was compared beat-by-beat with cutaneous vascular resistance ( CVR) derived by dividing mean blood pressure of the left third finger by cu taneous blood flow of the left fourth finger. The correlations overall at t he three temperatures between log DNPVLF and log CVRLF (LF, law frequency c omponent of DNPV and CVR) ranged From -0.89 to -0.96 among the subjects. Af ter adjusting for a maximal extension of the vascular wall (DNPVmax), the c orrelations became stronger. It was concluded that DNPV was a reliable and valid indicator of vascular tone in the finger.