Estimation of pulse transit time using two diametric blood pressure waveform measurements

This paper presents a novel method to estimate the aortic-to-peripheral pulse transit time (PTT) using the blood pressure waveforms measured at two diametric peripheral locations, for instance, one on an upper extremity and the other on a lower extremity. The method is based on a computational relationship between the two peripheral blood pressures, which is derived by first relating each peripheral blood pressure to a common central aortic blood pressure. The parameters of the computational relationship for an individual subject can be identified by fitting them to two peripheral blood pressure waveform measurements, thereby characterizing the cardiovascular dynamics, from which absolute changes in the PTT between the central aorta and each peripheral measurement site can be determined. The strength of the method is that it does not require any a priori knowledge of the peripheral measurement locations nor of the physiologic condition of the cardiovascular system. Experimental results are provided from five healthy swine subjects whose actual PTT experimentally varied from 44.9 ms to 163.0 ms (76.7 ms mean+/-26.4 ms SD). Compared to the reference PTT measurement, the novel method proposed in this paper estimated PTT within 3.7 ms mean+/-4.2 ms SD after initial calibration.