Cardiorespiratory coupling evaluation using smart-eyewear technology: a preliminary study

This study explores the feasibility of smart-eyewear (SEW) technology to automatically extract cardiac and respiratory signals by head-ballistocardiography (H-BCG) and to assess cardiorespiratory coupling during a paced breathing protocol. In 7 healthy subjects, H-BCG was recorded using an inertial sensor integrated in the SEW prototype. Simultaneously, ECG was acquired as a gold standard. After filtering, respiratory and cardiac components were derived to detect breathing cycles and heartbeats, enabling extraction of temporal and morphological parameters. A folded scattergram approach was applied to visualize changes in these parameters across the respiratory cycle, and differences between metrics were statistically evaluated. Respiratory cycle detection showed higher feasibility at respiratory rates of 6 and 8 seconds per respiratory cycle. Respiratory phase and rate dependences for both morphological and temporal H-BCG parameters were observed. These findings highlight the potential of S-EW technology for monitoring cardiorespiratory coupling in real-world scenarios, potentially including spontaneous breathing.