The beat-to-beat relationship between pulse transit time and systolic blood pressure

Non-invasive measurement of beat-to-beat arterial blood pressure (BP) is an interesting but currently unsolved topic in long-term physiological monitoring by wearable devices and body sensor networks. Although it is suggested that pulse transit time (PTT) is related to and can be used to estimate BP, few studies showed how their relationship changes over time. This study reported the beat-to-beat correlation between PTT and invasive BP of short segments for 4 subjects during an 8-hour period. The results of the study found that the median correlation of beat-to-beat PTT and invasive BP decreased from -0.73 to -0.63 when the number of consecutive beats used to calculate the correlation increased from 15 to 360, suggesting that PTT-based techniques may need frequent calibration in order to estimate beat-to-beat BP.