Pulse transmission time based on temporal difference in the instantaneous phase between electrocardiogram and photoplethysmogram signals

Analysis of the baroreflex characteristics is useful for the earlier detection of diseases such as hypertension. However, a continuous blood pressure signal must be measured with a comparatively-expensive device for this analysis. If information which has high correlation with the Mayer wave (0.05-0.15Hz) component of blood pressure can be obtained by an easy method, it will be possible to estimate the baroreflex characteristics in equipment for home healthcare and telemedicine systems. In this study, pulse transmission time (PTT), which is known to be correlated with blood pressure, was calculated by using not only a traditional method but also a new algorithm based on the temporal difference in the instantaneous phase between electrocardiogram and photoplethysmogram signals. Analysis of 94 healthy subjects' data showed that information which has a relatively high correlation with the Mayer wave component of blood pressure could be obtained from the two PTTs by selecting one of them on the basis of their powers in the Mayer wave-related band.