Development of Small and Lightweight Beat-By-Beat Blood Pressure Monitoring Device Based on Tonometry

Abstract

Blood pressure (BP) variability (BPV) is one of the important risk factors of cardiovascular (CV) disease. Particularly, nocturnal short-term BPV, characterized as acute transient BP elevation over several tens of seconds (BP surge), can trigger CV events. To accurately detect BP surge, it is necessary to monitor BP at each heartbeat. Although continuous BP monitors have been developed and validated, they are too large to measure beat-by-beat (BbB) BP at home. Therefore, we developed a small and lightweight BbB BP monitoring device (BbB device) based on tonometry. In this study, the BbB device was evaluated in terms of size, weight, and performance compared with a validated conventional continuous BP monitoring device based on tonometry (conventional device). The performance was evaluated using the correlation coefficient of pulse wave signals and the difference in BbB BP values between the two devices. Measurement data obtained from 30 subjects with a total of 81 sets, including short-term BPV by the Valsalva maneuver, was used for the evaluation of the performance. The results showed that the conventional device consists of two units (a control unit and a sensor unit), while the BbB device has integrated them into a single unit, with a weight of 150 g (approximately 1/45th of the conventional device). The BbB device was significantly smaller and more lightweight than the conventional device. The correlation coefficient of pulse wave signals between the two devices was 0.98 ± 0.02. The BbB systolic BP and diastolic BP differences were -0.3 ± 4.7 mmHg and 0.7 ± 3.4 mmHg, respectively. The developed BbB device was demonstrated to have an almost equivalent performance as the validated conventional device. In conclusion, we realized a small and lightweight continuous BP monitor that can evaluate the BP for each heartbeat using the BbB device without limitations regarding measurement location. Our device can monitor changes in BP at each heartbeat and short-term BPV, which would be important index for preventing CV events.