Design and Validation of Dual-Point Time-Differentiated Photoplethysmogram (2PPG) Wearable for Computer Method in Cuffless Blood Pressure Estimation

Abstract

Background & Objectives: Measurement of blood pressure (BP) in ambulatory patients is crucial for at high-risk cardiovascular patients. A non-obtrusive, non-occluding device that continuously measures BP via photoplethysmography will enable long-term ambulatory assessment of BP. The aim of this computational study is to validate the metasense 2PPG cuffless wearable design for continuous BP estimation without ECG.Methods: A customized high-speed electronic optical sensor architecture with laterally spaced reflectance pulse oximetry was designed into a simple unobtrusive low-power wearable in the form of a watch. 78 volunteers with a mean age of 32.72 ± 7.4 years (21 to 64), 51% male, 49% female were recruited with ECG-2PPG signals acquired. The fiducial features of the 2PPG morphologies were then attributed to the estimator. A 9-1 K-fold cross-validation was applied in the ML.Results: The correlation for PTT-SBP was 0.971 and for PTT-DBP was 0.954. The mean absolute error was 3.167±1.636mmHg for SBP and 6.4± 3.9 mm Hg for DBP. The ambulatory estimate for SBP and DBP for an individual over 3 days with 8-hour recordings was 0.70-0.81 for SBP and 0.42-0.51 for DBP with a +2.65 mmHg for SBP and +2.02mmHg for DBP. For SBP, 98% of metasense measurements were within 15 mm Hg and for DBP, 91% of metasense measurements were within 10 mmHg.Conclusions: The metasense device provides continuous, non-invasive BP estimations that are comparable to ambulatory BP meters. The portability and unobtrusiveness of this device, as well as the ability to continuously measure BP could one day enable long-term ambulatory BP measurement for precision cardiovascular therapeutic regimens.

Note:
Funding Information: Nanyang Technological University, National Heart Centre Singapore, Singapore Health Technologies Consortium (HealthTEC.SG) (grant award 020442-00001), Singapore National Medical Research Council (NMRC) Open Fund Young Individual Research Grant (OF-YIRG) under the grant award (NMRC REQ0305234).

Conflict of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Ethical Approval: This study was approved by the ethics committee at Nanyang Technological University. Institutional Review Board, No: IRB-2023-875, Date: 14 December 2023. Written informed consent was obtained from all participants to participate in the study. Identifiable information was removed from the collected data to ensure anonymity of the participants.

Keywords: Photoplethysmography, Blood Pressure, Wearable Health Monitoring, Machine Learning, Electrocardiography, Signal Processing