Multimodal wearable chest device for cardiovascular metric monitoring

Cardiovascular diseases (CVDs) remain the leading cause of global mortality, with arrhythmias and hypoxemia among the contributors to adverse events. Continuous monitoring of these parameters, particularly blood oxygenation (SpO2) and heart rate is essential for proactive cardiovascular health management. However, current wearable technologies often lack accuracy, suffer from motion artifacts, require frequent calibration, and rely on intermittent tracking. To address some of these limitations, we present a multimodal wearable chest device that integrates photoplethysmography (PPG), electrocardiography (ECG), and strain gauge sensor to enable continuous, non-invasive cardiovascular monitoring. The optical design of the PPG modality uses red, infrared, and green LEDs in a reflectance configuration paired with a sensitive photodiode. This multiwavelength approach supports SpO2 estimation and pulse waveform acquisition across a range of skin tones. The addition of the ECG provides electrical heart rate and rhythm features, while a strain gauge-based mechanical plethysmography modality captures subtle chest wall deformations caused by cardiac contraction. The device was validated against clinical-grade reference systems: Masimo (PPG), Polar (ECG), and Finapres (BP). Testing was conducted on 3 participants under a dynamic protocol including respiration rate variations and breath holds to induce physiological variability. Results demonstrate a multimodal wearable platform that combines optical, electrical, and mechanical sensing for extraction of SpO2 (75-98%), heart rate (approximately 60-100 bpm), and respiration rate (5, 7, and 9 respirations/min), with mean absolute errors of 1.3-2.6 bpm for heart rate, 0.9-1.5 respirations/min for respiration rate, and SpO2 agreement within ±0.4-1.2% (mean ± STD) relative to clinical reference devices. Overall, the feasibility of a multimodal chest-mounted wearable for comprehensive cardiovascular monitoring was demonstrated.