SeismoWatch

Abstract

The current norm for measuring blood pressure (BP) at home is using an automated BP cuff based on oscillometry. Despite providing a viable and familiar method of tracking BP at home, oscillometric devices can be both cumbersome and inaccurate with the inconvenience of the hardware typically limiting measurements to once or twice per day. To address these limitations, a wrist-watch BP monitor was developed to measure BP through a simple maneuver: holding the watch against the sternum to detect micro-vibrations of the chest wall associated with the heartbeat. As a pulse wave propagates from the heart to the wrist, an accelerometer and optical sensor on the watch measure the travel time – pulse transit time (PTT) – to estimate BP. In this paper, we conducted a study to test the accuracy and repeatability of our device. After calibration, the diastolic pressure estimations reached a root-mean-square error of 2.9 mmHg. The watch-based system significantly outperformed (p<0.05) conventional pulse arrival time (PAT) based wearable blood pressure estimations – the most commonly used method for wearable BP sensing in the existing literature and commercial devices. Our device can be a convenient means for wearable BP monitoring outside of clinical settings in both health-conscious and hypertensive populations.1

An Estimation Method of Continuous Non-Invasive Arterial Blood Pressure Waveform Using Photoplethysmography: A U-Net Architecture-Based Approach

“…However, much research has stated that the R wave of ECG is not reliable to measure the beginning of a pulse, and the measuring equipment for ECG data acquisition is very complex and expensive, the sensors are also hard to find. In [ 13 ], a combination of PPG and seismocardiogram was applied in a wristwatch for SBP and DBP calculation. The device needed a high-resolution three-axis accelerometer sensor pressed to the sternum to measure heart vibrations.…”

Current Status and Prospects of Health-Related Sensing Technology in Wearable Devices

“…The PWV can be calculated by dividing the artery length with the pulse transit time (PTT) or pulse arrival time (PAT), which can be derived combining the feature points (peak, valley, peak of 1 st derivative, etc.) of electrocardiogram (ECG), photoplethysmogram (PPG) [39–46], phonocardiogram (PCG) [47], seismocardiogram (SCG) [48], and ballistocardiogram (BCG) [49, 50]. Sometimes the PTT and PAT are used as the same; however, the strict meaning of the pulse arrival time is the sum of pulse transit time and preejection period (PEP) [63].…”

Cuffless Blood Pressure Monitors: Principles, Standards and Approval for Medical Use

“…Other less well-known methods for measuring PAT and PTT include electrical bio-impedance (Bimp) [21][22][23][24], BCG [25][26][27][28][29], and seismocardiography (SCG) [30][31][32][33], To use Bimp, BCG, and SCG, specialized technology are required; no commercial medical devices are available.…”

“…SCG measures pericardial vibration during cardiac movement. It can monitor the PTT (with PEP excluded) and improve the conventional PTT analysis approach, but selection of the most appropriate measurement site can be difficult [30][31][32][33]. Ultrasound sensors are also used to measure BP and capture BP waveforms in relatively deep layers of arterial and venous sites {34-36}.…”