Work

SCRIBE Design and Validation: Simultaneous Cardiac and Respiratory Impedance Biomarkers With Electromechanics

Year: 2026

Type: article

Abstract: Chronic respiratory and heart diseases significantly impact the health and well-being of hundreds of millions of people worldwide. Wearable, continuous at-home monitoring could improve patient outcomes via early detection and monitoring of adverse incidents. Bioimpedance (BioZ) signals such as impedance pneumography (IP) and cardiac impedance plethysmography (cIPG) could enable continuous monitoring of both pulmonary and cardiac health. Validating these signals in compact electrode configurations can help inform design tradeoffs in wearable device form factors and provide insights into optimal placement on the body. In this work, we present SCRIBE: a compact, flexible, quad-modal chest patch that concurrently measures cardiac and respiratory mechanics using electrocardiography (ECG), seismocardiography (SCG), photoplethysmography (PPG), and BioZ. The$9.6\times 5$cm four-electrode array was validated against reference benchtop devices and acquires high-quality cIPG and IP signals in parallel with single-lead ECG at two central locations: the sternum and left subclavicle. Signal quality at peripheral subpectoral and midaxillary line placements was also examined. Using an established respiration signal quality index (SQI) pipeline, we demonstrate that at least 85% of patch IP breaths are of high quality at the sternum or beneath the clavicle and can be mapped 1–1 with high-quality spirometer breaths. Tidal volume (TV) estimated from patch-based IP signals was validated and predicted TV within a mean absolute percentage error (MAPE) of 12.5% using less than 2 min of spirometry calibration data per subject, enabling short calibration times. Respiration rate (RR) estimation is also reported. SCRIBE can acquire high-quality SCG, cIPG, and multiwavelength (green/red/IR) reflectance PPG from the sternum, which was confirmed using dynamic time warping (DTW) and dynamic time feature matching (DTFM) SQI algorithms. At this location, more than 92% of all SCG, cIPG, and green/red/infrared PPG beats were high quality. This is comparable to 95% and 99% of SCG and impedance cardiography (ICG) beats from reference instruments. ECG-derived heart rate (HR) and PPG/cIPG pulse rate (PR) were also examined. Across all locations, the sternum confers the best combination of cardiac and respiratory signal quality, with subclavicle placement as a viable alternative. At both locations, SCRIBE enables continuous estimation of TV, RR, and cardiac timings for potential early detection of both exacerbated breathing events and increased risk of cardiovascular events.

Source: IEEE Sensors Journal

DOI: 10.1109/jsen.2026.3702932