Upper-Arm Photoplethysmographic Sensor with One-Time Calibration for Long-Term Blood Pressure Monitoring

Abstract

Wearable cuffless photoplethysmographic blood pressure monitors have garnered widespread attention in recent years; however, the long-term performance values of these devices are questionable. Most cuffless blood pressure monitors require initial baseline calibration and regular recalibrations with a cuffed blood pressure monitor to ensure accurate blood pressure estimation, and their estimation accuracy may vary over time if left uncalibrated. Therefore, this study assessed the accuracy and long-term performance of an upper-arm, cuffless photoplethysmographic blood pressure monitor according to the ISO 81060-2 standard. This device was based on a nonlinear machine-learning model architecture with a fine-tuning optimized method. The blood pressure measurement protocol followed a validation procedure according to the standard, with an additional four weekly blood pressure measurements over a 1-month period, to assess the long-term performance values of the upper-arm, cuffless photoplethysmographic blood pressure monitor. The results showed that the photoplethysmographic signals obtained from the upper arm had better qualities when compared with those measured from the wrist. When compared with the cuffed blood pressure monitor, the means ± standard deviations of the difference in BP at week 1 (baseline) were −1.36 ± 7.24 and −2.11 ± 5.71 mmHg for systolic and diastolic blood pressure, respectively, which met the first criterion of ≤5 ± ≤8.0 mmHg and met the second criterion of a systolic blood pressure ≤ 6.89 mmHg and a diastolic blood pressure ≤ 6.84 mmHg. The differences in the uncalibrated blood pressure values between the test and reference blood pressure monitors measured from week 2 to week 5 remained stable and met both criteria 1 and 2 of the ISO 81060-2 standard. The upper-arm, cuffless photoplethysmographic blood pressure monitor in this study generated high-quality photoplethysmographic signals with satisfactory accuracy at both initial calibration and 1-month follow-ups. This device could be a convenient and practical tool to continuously measure blood pressure over long periods of time.

Benchmarking of Sensor Configurations and Measurement Sites for Out-of-the-Lab Photoplethysmography

“…Similarly, the upper arm site demonstrated values comparable to the wrist locations, justifying its use in blood pressure estimation [ 73 ]. In contrast, the ankle sensor exhibited poorer results, characterized by higher spectral entropy, lower wave morphology similarity, and reduced sensitivity to systolic peaks.…”

Recent Advances in Materials, Devices and Algorithms Toward Wearable Continuous Blood Pressure Monitoring

“…The benefits of noninvasiveness, convenience, and efficiency make the PPG broadly utilized in PW monitoring for clinical practice. Numerous research teams are also diligently leveraging PPG to develop high-performance wearable PW sensors. ,, These PW sensors can function in various body locations such as fingers, wrists, − arms, , and earlobes. , Among these body locations, PPG sensors on the wrists are undoubtedly the most convenient and unobtrusive measuring devices to users. In this regard, PPG sensors in wristwatch format consisting of two PPG sensors and other sensors, i.e., pressure sensors and temperature sensors, were designed for multichannel PW signals, wearing pressure, and skin temperature detection (Figure B) .…”

Wearable Sensors as a Preoperative Assessment Tool: A Review

“…( d ) An upper-arm PPG sensor utilising reflective PPG detection, similar to that used in preoperative monitoring research [ 119 ]. The figure is taken as part of a larger figure from Wang et al (2023), Creative Commons Attribution International 4.0 License [ 92 , 120 ]. ( e ) The Fitbit Inspire collects a combination of accelerometer and PPG data from the user and is commonly used in preoperative research.…”