Pulse Transition Time Method for Unobtrusive Blood Pressure Estimation

Abstract

Pulse Transition Time (PTT) is being increasingly used for estimating blood pressure unobtrusively aiming at continuous assessment of cardiovascular diseases (CVD) and illness monitoring using portable and low-cost equipment. Several methods are available for PTT estimation, each one accepting its own constraints and physical parameters’ assumptions, besides the panoply of definitions attributed to PTT calculus. Defining PTT as the time difference between the time instant were peak R occurred in an electrocardiogram (ECG) cardiac cycle and the time instant were the photoplestimography (PPG) signal of correspondent cardiac cycle presents the inflexion point of its maximum slope, a method of PTT estimation based on measured ECG and PPG signals during several cardiac cycles is proposed. This method was tested on ECG and PPG data collected from 7 individuals for periods ranging from 30 min to 8 h. For the sake of PTT algorithm performance evaluation, ECG and PPG signals were collected with a commercial system, together with the PTT signals provided by the same equipment resultant from automatic computation with unknown algorithm. Preliminary results so far obtained encourage the use of the proposed PTT estimation algorithm on future internet of things (IoT) e-health system development aiming at elderly blood pressure estimation and CVD assessment. Accuracy of the proposed algorithm (0.9 correlation with reference signal) may be improved by further studies on raw data filtering parametrizations.