Vasoactivity influence on noninvasively determined regional peripheral compliance

The effect of vasoactivity on a noninvasive technique for measuring regional peripheral vascular compliance was investigated by applying the cold-pressor test (CPT). Compliance was measured at the finger by detecting an infrared photoplethysmographic waveform, as an indicator of intravascular volume change, and a continuous blood pressure waveform, as obtained by the vascular unloading technique. The signals were recorded at heart level, on a multichannel analog recorder, while the subject remained seated. A total of 15 healthy volunteers (24–68 yrs.) participated in the study. There was a 60–85% decrease in compliance in twelve individuals in response to the CPT test, while a slight decrease (up to 15%) was observed in the remaining three individuals. These three subjects had photoplethysmographic waveforms whith much smaller amplitudes than the other twelve participants before applying the CPT test.