A pulse wave velocity estimation method for a wearable monitoring device: feasibility and preliminary experimental results

The continuous monitoring of pulse wave velocity (PWV) - an indicator correlated to arterial stiffness, vascular aging, and blood pressure - is receiving growing interest. In a clinical setting, ultrasound allows an accurate assessment of the PWV from the arterial longitudinal section, acquired at high frame rate (HFR). However, it requires a careful and stable alignment between the probe and the vessel itself, which cannot be guaranteed with wearable sensors. In this work we propose a proof-of-concept system to measure PWV using two linear arrays scanning two arterial cross-sections. In principle, they could be integrated into a patch or small wearable device and could loosen the array-to-vessel alignment requirements and, thus, enable wearable applications. The system was proved by exploiting the ultrasound advanced open platform (ULA-OP 256), which was connected to a 7.5-MHz linear array. Experimental data were acquired when investigating different diameter vessels of a flow phantom, whose flow was controlled by a peristaltic pump, modulated by an electro-valve, and monitored by a pressure sensor. PWV estimates obtained with the proposed method lied within the reference method's uncertainty interval (Reference method PWV values: 12.4 +/- 2.65 m/s for 2-mm vessel and 10.4 +/- 1.81 m/s for 4-mm. Proposed method PWV estimates: 13.9 +/- 2.09 m/s for 2-mm vessel and 9.6 +/- 1.45 m/s for 4-mm).