Modeling of Pulse Transit Time under the Effects of Hydrostatic Pressure for Cuffless Blood Pressure Measurements

The pulse transit time (PTT)-based approach has been proposed as a noninvasive and cuffless alternative to the conventional occluding-cuff approaches to be used in wearable medical devices for long-term and continuous monitoring of blood pressure (BP). Nevertheless, the PTT-based technique requires an individualized calibration procedure. In order to derive a simple procedure for estimating individualized coefficients for this approach, this paper aims to model PTT under the effects of hydrostatic pressure due to hand elevation. In this study, 11 volunteers were recruited. BP and PTT were measured while the subjects elevated their hands to specific heights above heart level (h). The results of the study show that PTT changes significantly with h (p<0.05) and the relationship between them generally agrees with that derives from the theoretical model. This suggests that using the proposed model, individualized coefficients for estimating BP by the PTT-based approach can be obtained from some simple movements such as hand elevation.