Sub‑Second Hemodynamic Phase Shifts: Adaptive Multi‑Modal Fusion for Wearable Patches
The Challenge of Sub‑Second Hemodynamic Phase ShiftsWearable health patches promise continuous, non-invasive monitoring of cardiovascular dynamics, but they face a fundamental obstacle: hemodynamic phase shifts occur on sub-second timescales, yet most commercial sensors sample at rates too low to capture them. A typical photoplethysmography (PPG) sensor sampling at 25–50 Hz misses transient changes in blood volume that happen between beats—such as the rapid diastolic rebound or the subtle oscillations induced by respiration. This temporal blind spot leads to inaccurate estimates of stroke volume, arterial stiffness, and even heart rate variability (HRV) metrics that clinicians rely on for early warning of deterioration.Why Speed Matters in Hemodynamic MonitoringThe cardiovascular system is not a steady-state pump. Within each cardiac cycle, blood volume in peripheral tissues shifts in milliseconds due to arterial pulse propagation, venous return, and microvascular autoregulation. These sub-second shifts encode information about cardiac contractility, peripheral resistance, and even autonomic tone. When