Vascular Unloading Method for Noninvasive Measurement of Instantaneous Arterial Pressure: Applicability in Psychophysiological Research

A new method proposed previously by us (1980) was described to evaluate its applicability in psychophysiological research. In this method, beat-to-beat systolic and diastolic pressure as well as the pressure waveform can be measured noninvasively in the human finger. By use of a hydraulicservosystem, the photoplethysmographically detected vascular volume changes associated with intraarterial pressure in the finger are compensated by an applied counterpressure (cuff pressure) to maintain a proper value corresponding to the unloaded vascular volume. At this state the controlled cuff pressure follows instantaneously the intraarterial pressure. Comparison data were obtained by direct measurement of blood pressure in the brachial artery in 3 normotensive and 3 hypertensive subjects. High correlations between the two measures were obtained in each subject under various conditions. By maintaining circulation in the finger, this method enables the noninvasive and continuous measurement of instantaneous arterial pressure for more than one hour without much discomfort. This indirect method should be useful in many areas of psychophysiological research.