Eyewear-Based ECG Recording: A Novel Head-Electrode Approach for Reliable Cardiac Signal Acquisition

Recent advances in wearable technology have enabled the recording of electrocardiogram (ECG) signals from unconventional body locations, including the head. Particularly on this last location, ECG recording is challenging due to the low signal-to-noise ratio (SNR), making fundamental the selection of relevant positions on the head to gather high-quality signals. In addition, traditional wet electrodes are unsuitable, necessitating the use of dry electrodes. In this work, we investigated the feasibility of recording the ECG using a novel eyewear-based setup, enabling a single-lead high-quality ECG acquisition. The prototype featured three dry electrodes, strategically placed on an eyewear prototype, one in the nose pad (reference electrode), the second electrode (-) in contact with the ear pad skin and the third electrode (+) exposed on the external surface of the frame to be touched by the fingertip. Among various materials, we identified conductive elastomers featuring the most favorable impedance characteristics through measurements performed on gelatin compounds and human skin. The prototype was systematically tested against standard chest ECG in 25 participants to verify the quality of the ECG signal and the derived heart-rate variability (HRV) indexes. The recorded ECG signals were classified as Excellent, Barely Acceptable, and Unacceptable in 72, 28 and 0% of the overall cases. HRV indices obtained from both the prototype and standard ECG showcased a strong correlation (R >0.9). This study highlighted the feasibility of high-quality ECG recording based on eyewear setups.