Normalized pulse volume and blood volume as separate indices of finger arterial and venous vascular tone: Examination under propofol

This study examined the newly proposed indices for estimating finger vascular tone, which can be obtained from near infrared transmittance photoplethysmographic recordings; normalized pulse volume (NPV) and blood volume (BV). They were recorded for seven male and two female students under continuous infusion of and recovery from propofol. Concomitant hemodynamic measurements were made with a non‐invasive impedance cardiograph and a continuous blood pressure monitor. Normalized pulse volume showed no apparent dose‐dependency and was negatively correlated with total peripheral resistance. In contrast, BV increased dose‐dependently with propofol concentration and was negatively correlated with cardiac preload index (PLI) and with stroke volume (SV) at higher concentrations. The supplementary structural equation modeling procedure effectively illustrated causal relationships between BV, PLI and SV. In conclusion, the present data suggest that NPV and BV independently reflect arterial and venous tone in the finger tip, respectively. Although the underlying mechanisms remain unclear, BV is more sensitive to vascular dilation under propofol anesthesia.