An Unobtrusive Wearable Device for Ambulatory Monitoring of Pulse Transit Time to Estimate Central Blood Pressure

There is a clinical need for improved ambulatory, frequent and unobtrusive monitoring of blood pressure and cardiac parameters like systolic time intervals. Truly unobtrusive wearable devices combining impedance cardiography with other sensors may be one possible solution. The IsenseU-BP+ device presented in this article measures single channel ECG, impedance cardiography and photo plethysmography at the chest. The device also measures activity and posture, as well as skin temperature. In this study, we report on the possibility to use these signals to measure pulse transit time for estimating blood pressure changes. Six subjects has been tested. Four of them showed good correlation between PTT and mean arterial pressure while two of the subjects had too low signal to noise ratio in the photoplethysmography signal for good estimation of PTT. Thus these results show that the quality of the raw data is promising for calculating a pulse transit time that shows good coherence with mean arterial pressure.