A novel method to estimate baroreflex sensitivity based on pulse transit time

Baroreflex sensitivity (BRS) has emerged as a prognostic factor in cardiology. Spontaneous sequence technique is one of the most commonly used methods in measuring BRS. The technique requires continuous beat-to-beat blood pressure (BP) which, however, cannot be obtained conveniently. Considering that pulse transit time (PTT) is inversely related to BP and can be easily and continuously acquired from electrocardiogram (ECG) and photoplethysmogram (PPG), we proposed in this study a novel method that estimates BRS from PTT based on the sequence technique with low-pass filtering. The experiment was conducted on 25 healthy subjects from whom continuous BP, PTT and R-R interval (RRI) of ECG were obtained before, during and after drinking 400 ml of water. SBP-based BRS and PTT-based BRS were separately calculated. The results showed high correlations between these two BRS estimates in all situations (correlation coefficient γ=0.90, 0.70 and 0.81 before, during and after drinking respectively). Furthermore, results from both methods indicate that BRS increased significantly (p<;0.01) after water drinking.