A New Image Blood Pressure Sensor Based on PPG, RRT, BPTT, and Harmonic Balancing

A new blood pressure (BP) sensor, also named sphygmomanometer, is developed in this paper for estimating BPs accurately from fingertips. The hardware of the sensor is a low-cost optical CMOS imaging device for detecting photoplethysmography (PPG) signals at fingertips. Therefore, the sensor neither needs to contact human skin nor pressurize it for accurate BP predictions. To calculate BPs based on captured PPG signals, the modified radial resonance theory is applied to develop a new BP transport theory (BPTT), and then composes a computation algorithm for implementing BPTT in a typical smart phone with limited computation load required. The algorithm is successfully implemented in a typical smart phone with minimum computation load and equipped with an efficient calibration process. An experiment is conducted to evaluate the performance of the designed BP-sensing techniques. The resulted data clearly show that the difference between the systolic BPs (SBPs) sensed by the propose sensor and a validated cumbersome instrument is 1.37 mmHg, while for diastolic BPs (DBPs) is -1.40 mmHg. The afore-reported accuracy is well below those required by the Association for the Advancement of Medical Instrumentation, which are ±5 and 8 mmHg, respectively, for SBPs and DBPs.