Development of a mobile phone based beat-by-beat sphygmomanometer

This paper is aimed at the development of a high-precision, noninvasive, continuous blood pressure monitor using pulse arrival time (PAT). A continuous putative function of systolic blood pressure was realized using Electrocardiogram (ECG) and the pulse signals for calculating the pulse wave are obtained from electrodes that are attached to both hands and a photoplethysmographic sensor attached to the tip of the finger and the hand. First, noise such as drift, electromyogram, and hum noise is reduced using a notch filter and a bandpass filter. Next, the QRS wave peak of the ECG is detected. In parallel with QRS wave peak detection, the leading edge of the pulse is detected. The interval between these two points is computed as the PAT. Then, the signal most correlated to change in blood pressure is selected. In this way, systolic blood pressure is computed continuously and precisely.