Monitoring Autonomic Tone During Spinal Cord Neuromodulation Using Wearable AURIS Sensor

The transition of bioelectronic medicine to clinical use is currently limited by a lack of non-invasive sensors capable of measuring autonomic tone during active neuromodulation. Conventional monitoring modalities, such as mean arterial pressure (MAP) and Ag/AgCl chest electrodes, are often invasive, cumbersome, or motion-prone. Here, we present a framework employing an in-ear sensor (AURIS) to continuously monitor heart rate variability (HRV) during neuromodulation. These sensors use a polydimethylsiloxane (PDMS) and PEDOT:PSS composite to ensure biocompatibility and superior conformability. Experiments in a rodent model (n = 3) indicate that the AURIS platform reproduces the gold-standard chest electrodes for the mean-level and normalized HRV metrics used to assess autonomic tone, with no significant difference between modalities (e.g., Mean RR p = 0.997, Mean HR p = 0.991). Agreement was weaker for the absolute spectral-power metrics, consistent with a higher noise floor in the auditory canal that nonetheless leaves beat-to-beat timing intact. During thoracic focused ultrasound, the platform showed a consistent trend suggestive of an autonomic shift: no metric reached significance at this preliminary sample size, but several showed medium-to-large effect sizes in a coherent direction, led by SD2 (d = 0.708), SD1/SD2 (d = 0.630), SDNN (d = 0.569), and Mean RR (d = 0.521). As a proof of concept, these findings support a durable, accessible, non-invasive sensor architecture for autonomic monitoring and provide a technical foundation for closed-loop feedback and future adequately powered studies.