A correlation study on the variabilities in pulse transit time, blood pressure, and heart rate recorded simultaneously from healthy subjects.

This paper proposes to use the pulse transit time variability (PTTV) as an indicator of the variability in hemodynamics and studies its correlation with other cardiovascular variabilities, especially the blood pressure variability (BPV), which receives increasing attentions as an independent indicator of autonomic regulation and abnormalities in cardiovascular system. Continuous blood pressure (BP), electrocardiogram (ECG), and photoplethysmographic (PPG) signal were collected simultaneously from 11 healthy subjects in resting state. Two types of pulse transit time (PTT), defined by different characteristic points of ECG and PPG signals, were measured beat by beat noninvasively. Correlation coefficient was employed to quantify the relationship between the beat-to-beat variabilities in any pair of the target cardiovascular parameters. Significant correlations were consistently observed among the variabilities in systolic BP, pulse BP and PTT<inf>f</inf>, which was defined as the time interval between the peak of ECG R-wave and the frontal foot of the PPG pulse within the same cardiac cycle. The results of this study indicate that variability in PTT<inf>f</inf>is highly associated with that in BP and can be potentially used for BPV estimation for healthy subjects at static body state.