Development and Characteristics of Portable Spatial Pulse Wave Velocity Monitoring Device Composed of MPG and PPG

To monitor peripheral vascular conditions, we developed a portable measurement device that utilizes a magnetoplethysmogram (MPG) sensor implemented using a permanent magnet and a Hall element together with a photoplethysmogram (PPG) sensor to acquire peripheral pulse waveforms. The user’s hand length (L_H) divided by the temporal delay (Δτ) between two peaks of pulse signals obtained from the two sensors is used to calculate the spatial pulse wave velocity (SPWV). Analysis of the MPG and PPG output waveforms demonstrated stable, clearly periodic signals. We confirmed a meaningful property of SPWV from the preliminary pilot study measured by using the SPWV1 and SPWV2 monitoring devices. The difference between SPWV1 and SPWV2 arises from the pulse period correction. Because Δτ_ave2 = Δτ_ave1 + T_period, the denominator in the SPWV2 calculation increases, resulting in characteristically smaller SPWV2 values. For participant #1, SPWV1 remained within a relatively narrow band of 2.8 m/s~2.9 m/s, and SPWV2 within 27 cm/s~28 cm/s over the 60 min measurement window, demonstrating stable behavior. For participant #2, SPWV1 showed greater variability, increasing to a maximum at approximately 40 min before decreasing, while SPWV2 remained within 24 cm/s~26 cm/s. The SPWV measurement system based on MPG-PPG is expected to enable convenient, non-invasive monitoring of peripheral vascular health.