The application of calibrated photoplethysmography in conjunction with induced changes in leg hydrostatic pressure proved to be an effective physiologic method to noninvasively quantify venous hemodynamics in normal control subjects, patients with venous valvular insufficiency, venous obstructive disease, or both.
The application of calibrated photoplethysmography in conjunction with induced changes in leg hydrostatic pressure proved to be an effective physiologic method to noninvasively quantify venous hemodynamics in normal control subjects, patients with venous valvular insufficiency, venous obstructive disease, or both.
In view of the resemblance of exercise-induced plethysmographic changes with those obtained by direct venous pressure measurement, we decided to use a combination of photoplethysmography (PPG) and hydrostatic pressure calibration to determine the PPG/pressure relationship. A standard foot dorsiflexion exercise involving stepwise position changing was performed which induced hydrostatic pressure changes that were recorded as the heart-probe distance. A logarithmic PPG/pressure relationship was identified and the resulting ambulatory venous pressure (AVP) was obtained from the PPG/pressure curve. Simultaneous direct AVP was recorded in 14 patients scheduled for venous surgery. 'Non-invasive AVP only' was determined in 24 normal control subjects with a mean value of 19.24 mmHg (+/-8.79 SD). In the patient group, the direct AVP values were 40.00 mmHg (+/-10.83 SD) compared with the PPG values of 33.07 mmHg (+/-12.94 SD). The resulting correlation was r = 0.8850. By utilizing stepwise leg elevation, a reliable PPG/pressure curve can be established which, in turn, permits AVP determination. It is suggested that this non-invasive AVP determination may serve as a screening test to evaluate non-invasively venous hemodynamics.
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