method of PTT(Pulse transit time)estimation. PTT was defined as duration time from chest vibration to Plethysmogram(PTG)and PTT'was defined from Electrocardiogram(ECG)R-wave to PTG respectively. The measurement showed the difference between PTT and PTT'was negligible. Therefore, it is possible to use the time from ECG R-wave to PTG for PTT. This result shows consistent tendencies with previous findings. The Present method makes it easier to estimate PTT because of the high S/N ratio of ECG waveform. Some problems of practical application are also discussed.
