WearICG: Towards A Wearable Approach to Continuous Stroke Volume Monitoring

Abstract

Wearable devices have made continuous monitoring of basic vitals such as Heart Rate (HR), Heart Rate Variability (HRV), oxygen saturation (SpO2), single-lead electrocardiogram (ECG) routine, but the advanced hemodynamic markers needed to anticipate cardiovascular events remain confined to the clinic. Stroke Volume (SV) is among the most actionable of these markers: it is a leading indicator of acute hemodynamic decline that frequently drops before heart rate compensates, yet it is not directly accessible from photoplethysmography (PPG) or ECG. Impedance Cardiography (ICG) is the principal non-invasive electrical modality that captures central thoracic volume change, but its standard neck--thorax electrode geometry is incompatible with a chest-patch form factor. We present WearICG, a paired within-subject evaluation of chest-only ICG for SV estimation. Three chest-only electrode configurations are systematically compared against the standard neck--thorax reference, and SV estimation is validated against an FDA-cleared continuous Non-Invasive Blood Pressure (NIBP) reference (BIOPAC NIBP100D) across 17 participants and 5 hemodynamic perturbation states. The Inline-Chest configuration tracks neck--thorax with r = 0.91 ± 0.07. Following a short per-(subject, site) reference calibration at fit time, a mean-bias correction adapts classical Bernstein-family SV equations to chest geometry, raising the SV correlation against reference from r = 0.44 to r = 0.74. Together with the open evaluation code, these results establish a reproducible baseline for placement-aware modelling of chest-only ICG in next-generation cardiac patches.