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Research question: Surgical manipulation in cochlear implantation can generate traumatic intracochlear pressure transients [1]. At present, these pressure changes cannot be measured in vivo. To address this limitation and enable real-time surgical feedback, we propose and validate a non-invasive, surgically applicable approach for estimating intracochlear pressure transients.

Methods: We estimate intracochlear pressure transients by measuring pressure variation in the external auditory canal, exploiting reverse pressure transmission through the ossicular chain. The setup consists of an infrasound microphone coupled to the ear canal via a non-compliant tube and an ear tip. A customised acquisition software setup enables the synchronised recording of pressure and surgical video, allowing for precise temporal labelling of surgical manoeuvres. System functionality was validated by gentle tapping of the incus and pressure was monitored during the pre-insertion, insertion, and post-insertion phases.

Results: Recordings were obtained from 10 cochlear implant surgeries, with successful system validation in all cases. Across all surgical phases, we identified frequent pressure transients related to manoeuvres such as implant re-grasping, aspirator usage, and sealing of the facial recess, consistent with previous in-vitro and ex-vivo findings. During insertion, a spectral correlation was observed between the implant motion extracted from the surgical video and the measured pressure signal. A continuous pulsatile component corresponding to the heart rate was observed in all recordings.

Conclusions: We present a simple, non-invasive system for estimating intracochlear pressure transients that could enable direct surgical feedback during cochlear implantation. We validated the feasibility of the acquisition setup in vivo and observed clear signatures of intracochlear pressure transients from the ear canal pressure. Further signal processing is required to improve the isolation of intracochlear pressure transients from the physiological cardiac component.

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