A novel system for continuous peripheral arterial pressure-volume loop measurement

This study develops a system to obtain continuous blood pressure signal and impedance plethysmography (IPG) signal, simultaneously. Based on the principle of impedance measurement, the peripheral vessel volume change can be computed from the IPG signal. Equipped with simultaneous information of pressure and volume, a pressure-volume (PV) loop can be constructed. It is well known that the left ventricular pressure-volume loop contains a number of feature points indicating the performance of cardiac function. Therefore, in this study, the same principle is used to try to discuss the peripheral vessel pressure-volume loop. Ten volunteers were recruited for this study. Subjects went through the cold pressor test by immersing their left foot into ice water. Blood pressure signal and impedance changed were recorded using a custom-made system. The results illustrated that the pressure-volume loop, as it was expected, demonstrated a contraction phenomenon after stimulation in five out of ten subjects. The areas of those pressure-volume loops reduced as much as 70% in some subject. However, loop responses to stressors varied from subject to subject and the slope of the loop did not alter significantly. In conclusion, the proposed system is a potential way to measure and to investigate the compliance and characteristic of peripheral blood vessel.