A proof-of-concept wearable photoplethysmography sensor-node for near real-time pulse transit time measurements

Use of pulse transit time for estimating blood pressure is a promising method that could potentially address the pressing need for an unobtrusive and continuous blood pressure measurement technique. In this paper, we present a novel wearable smart sensor-node system that captures and transmits the distal timing information of pulse waves to a remote location for near real-time pulse transit time measurements. The proof-of-concept system monitors photoplethysmography signals captured from finger, identifies the foot-points of the waveforms, and transmits the timing information of the foot-points to a receiver over a free-space optical channel. Measurements from one healthy subject show that the average time difference between the distal timing information received in near real-time and calculated off-line is 34±6.2 ms. Supplied by a single 5 V power supply, the proof-of-concept system consumes 190 mW.