Does a wearable vital signs monitor at the ear using Pulse Transit Time improve tracking of mean arterial blood pressure changes compared to the pulse arrival time method?
A novel ear-worn wearable device measuring ECG, BCG, and PPG can effectively track changes in mean arterial blood pressure using Pulse Transit Time.
A continuous, wearable and wireless vital signs monitor at the ear is demonstrated. The device has the form factor of a hearing aid and is wirelessly connected to a PC for data recording and analysis. The device monitors the electrocardiogram (ECG) in a single lead configuration, the ballistocardiogram (BCG) with a MEMS triaxial accelerometer, and the photoplethysmograms (PPG) with 660 nm and 940 nm LED sources and a static photocurrent subtraction analog front end. Clinical tests are conducted, including Valsalva and head-up tilt maneuvers. Peak timing intervals between the ECG, BCG and PPG are extracted and are shown to relate to pre-ejection period and mean arterial blood pressure (MAP). Pulse Transit Time (PTT) extracted from cross-correlation between the PPG and BCG shows improved results compared to the pulse arrival time (PAT) method for tracking changes in MAP.
Winokur et al. (Wed,) studied this question.