Can the Timing-Characteristics of Phonocardiographic Signal be Used for Cuffless Systolic Blood Pressure Estimation?

Continuous and non-invasive measurement of blood pressure (BP) is always important to critically ill patients. To achieve continuous and cuffless BP monitoring, pulse transit time (PTT) has been reported as a potential parameter. Recently a novel parameter RS₂ (defined as the time interval measured from the R wave of electrocardiographic (ECG) signal to the peak of second heart sound of phonocardiographic (PCG) signal) is proposed for the same purpose. In this study, the relationship between systolic BP (SBP) and PTT as well as the relationship between SBP and RS₂ on 25 healthy subjects, aged 24plusmn3 years, were compared after exercise. The results in current study showed that SBP is correlated with both PTT and RS2, where the mean individual correlations are r=-0.95 and r=-0.85 respectively. The mean standard deviation of the differences between the measured SBP and the SBP predicted from the regression lines in scatter plots of SBP~PTT and SBP~RS₂ are 4.1 mmHg and 7.2 mmHg respectively. In summary, the results showed that RS₂ is possible to be used for continuous and non-invasive monitoring of SBP after exercise. In the future, it is important to investigate more robust techniques for locating characteristic points on the PCG signals