Blood Pressure Estimation Using a PPG Signal Recorded From the Fingertip of a Hand Moving in the Sagittal Plane

Abstract

In this paper, we present a new photoplethysmogram (PPG)-based Blood Pressure (BP) estimation approach, in which, the PPG recording site (fingertip) is not in a standstill position, but swings up and down in the sagittal plane during the recording. The upward and downward movements of the recording site result in useful morphological changes in the PPG signal, which can be used to better estimate BP. To investigate the effect of the vertical hand movement on the shape of the PPG signal, we first devised a PPG recording hardware and used it to collect a dataset consisting of PPG signals recorded from 120 subjects. Then, we utilized machine-learning models to estimate BP using the extracted features from the recorded PPG signals. The mean absolute and the standard deviation of the error for systolic and diastolic BP estimations were 6.63±5.59 mmHg and 3.96±3.82 mmHg, respectively. The results comply with the AAMI standard for BP measurement. They also achieve Grade A for diastolic, and Grade B for systolic BP and mean BP, based on BHS standard. We conclude that the changes in PPG signal morphology provide more informative features resulting in more accurate BP estimation compared to using PPG signals recorded from a standstill finger. Moreover, the proposed BP estimation method has great potential for implementation in smartphones to monitor BP more accurately than the previous methods in which the recording site is in a standstill position.