A Wearable and Flexible Photoplethysmogram Sensor Patch for Cuffless Blood Pressure Estimation With High Accuracy

Hypertension is a very significant public health problem and has become a potential risk for cardiovascular and renal diseases. Blood pressure (BP) including systolic BP (SBP) and diastolic BP (DBP) is a vital parameter that should be monitored regularly for the early detection and prevention of chronic diseases. The traditional cuff-based BP monitors can cause discomfort to the users due to inflation and deflation. Here, a wearable and flexible photoplethysmography (PPG) patch sensor based on the polydimethylsiloxane (PDMS) substrate and double-layer serpentine structure with a closed loop that can omit the transfer printing process is proposed for cuffless BP estimation. Three models are adopted to estimate the BP. The accuracy of SBP and DBP obtained are 3.68 ± 2.37 and 4.9 ± 3.78 mmHg for the first model and 3.61 ± 2.62 and 4.72 ± 3.46 mmHg for the second model, respectively. The third model introduces the Kalman filtering to optimize the solution of the coefficients of the second model to forecast BP. As a result, the accuracy of SBP and DBP as high as 2.94 ± 2.35 and 3.41 ± 2.94 mmHg, respectively, is realized. The results show that the introduction of the Kalman filter algorithm to forecast BP can not only reduce the number of calibrations, but also improve the accuracy of BP estimation.