Non-Invasive System to Deliver Therapeutic Hypothermia for Protection Against Noise-Induced Hearing Loss

Noise-induced hearing loss (NIHL) is highly prevalent among occupationally at-risk service groups like the military and firefighters, with disabilities that result in significant healthcare burden, negatively impacting performance on duty and quality of life. Exposure to noise can cause permanent threshold shifts (PTS) with accompanying hair cell loss, or temporary threshold shifts (TTS), with no evident hair cell loss. Noise exposure can also result in rapid and permanent loss of synaptic elements and cochlear nerve terminals with irreversible hearing impairment and long-term degeneration of spiral ganglion (SG) cell bodies. Currently no FDA-approved treatments are available to prevent or treat NIHL. Delivering pharmaceutical compounds over time, identification of safe dosages, and a critical timeframe relative to noise-exposure remain clinically challenging. RestorEar Devices LLC has developed a non-pharmaceutical application of mild therapeutic hypothermia (MTH) to protect residual sensory structures and function of the cochlea. MTH is a proven and well-established therapy for neuroprotection. This approach for MTH application is based on significant prior and on-going research that highlights its utility for residual hearing preservation against cochlear implant surgical trauma, ototoxicity, and noise exposure. With SBIR Phase I support, the investigators have successfully demonstrated that effective non-invasive, non-pharmaceutical therapeutic hypothermia can be delivered to the inner ear sensory structures. The investigators have built, calibrated, and tested ReBoundTM, a headband with cooling gel packs placed in contact with the surface of the mastoid. ReBoundTM delivers MTH safely and repeatedly for up to 30 minutes. In this study, the investigators aim to extend this application to human subjects and test safety and efficacy against NIHL in noise-exposed firefighters and matched controls with the collaboration of researchers at the University of Miami. Aim 1: Evaluate safety of MTH with ReBoundTM devices. With the first in-human studies, the investigators aim to show that MTH can be safely delivered to the inner ear using ReBound. In a randomized study, non-firefighter control subjects will receive MTH-treatment and normothermia-sham (non-cooled gel pack) through the device alternated over 8 sessions. Subjective assessments and audiologic testing (pure tone audiometry, auditory brainstem responses, distortion product otoacoustic emissions and electrocochleography) pre- and post-treatments will be compared between MTH-treatment and sham in each subject. Results of Aim 1 will support the hypothesis that this approach will deliver therapeutic hypothermia to the cochleae and that repeated application will not negatively affect hearing function in healthy subjects. Aim 2: Validate efficacy of the ReBoundTM MTH devices for mitigating NIHL in an occupationally at-risk group. Based on strong preliminary results, the investigators hypothesize that acute application of MTH in noise-exposed firefighters will reduce temporary changes in auditory function. Firefighters will be divided equally into two treatment groups, MTH-treatment and normothermia-sham. These treatments will be delivered with ReBound, with and without cooled gel packs, applied post-duty. MTH-treatment will also be applied in an age- and sex-matched control group over the same duration. Baseline hearing function will be measured prior to initiation of the treatment. Treatments and the functional assessments will be repeated quarterly over one year. Temporary and permanent threshold changes in this chronically the noise exposed group of firefighters receiving MTH-treatment will be compared with firefighters receiving sham-treatment and with controls receiving MTH-treatment. MTH-groups will also be sent home with a ReBound band and instructed to use it after noise exposure. Subjective assessments will be sent weekly to these groups to evaluate the use pattern of the device. Results of these studies will firmly establish MTH for mitigating NIHL. This research will be highly impactful given the significant adverse effects of NIHL, an unmet clinical need, and the high translational potential of MTH for mitigating NIHL.