Wearable Acceleration Plethysmography for Carotid Pulse Pressure Monitoring: A Feasibility Study

Central blood pressure (CBP), which is the pressure at the aorta and other central arterial sites such as the carotid, is more predictive of target organ damage and future adverse events, as opposed to conventional blood pressure assessed at more peripheral sites. However, methods to estimate CBP are complex, require frequent calibration and are not suitable for continuous tracking purposes. Here, we introduce a wearable accelerometer based pressure sensing system to track carotid pulse pressure (PP). The wearable system detects the transcutaneous pressure (P_T) on the skin surface over the carotid artery and identifies the key fiducial points (g₁, g₂). In-vivo study on 11 subjects showed that the peak-to-peak value, ΔP_T and maximum value, g₂ of P_T have a statistically significant and strong correlation with carotid PP (r = 0.75, p < 0.05) and SBP (r = 0.78, p < 0.05) respectively. The magnitude response (percentage mean difference between pre and post-exercise intervention) of P_T parameters (ΔP_T and g₂) were 78 % and 89 % as compared to 33 % and 19 % in carotid PP and systolic blood pressure (SBP), respectively. Reliability (SNR > 38 dB) and repeatability (CoV < 10%) were seen in the obtained transcutaneous pressure signals. The study limitation is identifying an appropriate calibration or model for carotid BP estimation. This study reveals the feasibility of using an acceleration plethysmogram (APG) based wearable pressure-sensing system for tracking changes in carotid PP and SBP which could pave the way for wearable systems for ambulatory assessment of central BP for clinical and home use.