Robust, beat-to-beat estimation of the true pulse transit time from central and peripheral blood pressure or flow...

We proposed a technique for estimating beat-to-beat pulse transit time (PTT) from central and peripheral blood pressure or flow waveforms based on an arterial tube-load model of wave reflection. The technique effectively estimates PTT from the entire waveforms after mathematically eliminating the reflected wave. So, unlike the conventional foot-to-foot detection technique, this technique should be robust to artifact while revealing the true PTT (i.e., the PTT in absence of wave reflection). We compared the two techniques, as applied to blood pressure and flow waveforms, in terms of the ability of their PTT estimates to correlate with blood pressure (a) during baseline (for which the naturally occurring beat-to-beat changes were small), (b) during low heart rate (wherein wave reflection was profound), and (c) in the presence of actual measurement artifact. In all three cases, the PTT estimates of the arterial tube-load model technique yielded markedly superior correlation to blood pressure.