Non-invasively determined ambulatory venous pressure.

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.