Long-Term Stability and Blood Pressure Change Tracking with a Cuffless Wearable Device in Hypertensive Patients

Demonstrating reliable tracking of short- and long-term blood pressure (BP) changes is one of the conditions necessary for clinical use of cuffless devices requested by international hypertension societies. This study evaluates the stability of BP estimation over a 6-week period using CSEM's wearable cuffless photoplethysmographic (PPG) BP monitor, and its ability in tracking BP changes in hypertensive patients when compared to a validated oscillometric monitor (Microlife WatchBP Home A).

In this method-comparison/feasibility study, thirty patients attended 4 visits over six weeks. During visits, BP was estimated as the median of 5 to 7 consecutive measurements performed with both the cuff-based (Cuff BP) and cuffless (PPG BP) devices. Between-visit systolic and diastolic BP changes (ΔSBP, ΔDBP) were assessed and compared using the mean ± standard deviation of the differences between devices to evaluate PPG BP stability. The concordance rate (CR), defined as the percentage of significant BP changes (ΔSBP > 15 mmHg, ΔDBP > 10 mmHg) showing a coherent direction between devices, was also assessed.

Thirty hypertensive participants (18/30 female; 54 ± 17years; BMI 29.2 ± 5.5kg/m²) were included. Mean differences between Cuff ΔBP and PPG ΔBP did not differ significantly over time, suggesting stability of PPG BP up to six weeks. Differences between Cuff BP and PPG BP were 0.2 ± 12.8mmHg for ΔSBP and -0.1 ± 7.4mmHg for ΔDBP. The CR for significant BP changes was 83% for SBP and 86% for DBP.

CSEM's wearable PPG-based cuffless BP monitor appears to provide stable BP estimation and concordant tracking of week-to-month BP changes during antihypertensive therapy when compared with an oscillometric device. High within-visit variability of the oscillometric device despite a standard protocol likely limited the comparison between both methods. These results, if confirmed in a larger sample and against a gold-standard reference, could support the clinical acceptance of PPG-based wearable BP monitors.