[Use of photoplethysmography with calibration in vivo for assessing venous hemodynamics of the lower extremity and particularly ambulatory venous pressure and refilling time after exercise].Helv Chir Acta. 1990 Jun; 57(1):161-7.HC
Several invasive and non-invasive methods are used actually for the appreciation of the morphology and the function of the venous system of the lower extremity. Hemodynamic parameters like the ambulatory venous pressure and the venous refilling time can not be determined without invasive measurements. This report describes the results of a prospective comparison of the ambulatory venous pressure and the venous refilling time with the in vivo calibrated photoplethysmography and with invasive measurements. Postural changes of hydrostatic pressure permitted in vivo calibration of the photoplethysmograph. We recorded quantitative photoplethysmography (PPG) ambulatory venous pressure and venous refilling time in 20 normal subjects, 20 patients with superficial varicosis and in 20 patients with chronic venous insufficiency. Quantitative photoplethysmography correlated closely with invasive measurements of ambulatory venous pressure with respect to estimated drop in superficial venous pressure and recovery time. PPG estimates of intravenous pressure in normal patients (24 +/- 9 mm Hg), in patients with varicosis (42 +/- 7 mm Hg) and post-thrombosis patients (63 +/- 9 mm Hg) agreed with ambulatory venous pressure measurements 22 +/- 9 mm Hg, 40 +/- 6 mm Hg and 61 +/- 6 mm Hg, respectively. Non invasive, quantitative photoplethysmography may prove to be an accurate estimate of ambulatory venous pressure in patients with superficial varicosis and in patients with chronic venous insufficiency.