Exploiting otoacoustic emission testing to identify clinical and subclinical inner ear barotrauma in divers: potential risk factor for sensorineural hearing loss.

INTRODUCTION: Divers may sustain subclinical inner ear barotrauma (IEBT) that is not identified on pure-tone audiometry (PTA) but is potentially an important contributor to chronic sensorineural hearing loss (SNHL). Otoacoustic emission (OAE) testing, which identifies transient emission shifts (TESs) stemming from noise-induced inner ear injury, may be a more sensitive measure than PTA. Recognizing the salubrious health implications in mitigating the incidence and severity of SNHL in divers with earlier detection, we performed a pilot study investigating the potential of OAEs to identify clinical and subclinical IEBT (defined as a TES without an accompanying transient threshold shift) in divers subject to a provocative repetitive diving protocol. METHODS: Eight US Navy-trained male divers participated in a repetitive diving protocol encompassing up to a maximum of 10 weeks of diving. All subjects received an otoscopic examination, tympanometry, and OAE testing on both ears prior to and immediately after each dive. Audiometry was evaluated prior to and after each week of repetitive diving. RESULTS: There were 212 data pairs for comparison in the OAE testing. The average group wideband transient-evoked OAE shift was -1.24 dB. Only 25 significant threshold shifts were identified in over 1000 comparisons via audiometry. CONCLUSIONS: OAE testing identified significant TES in a provocative repetitive diving protocol, supporting the assertion that both clinical and subclinical IEBT may contribute to chronic SNHL in divers. Exploiting this technology as an integral component of diving medical surveillance may identify those at risk for subsequent IEBT and hearing loss, facilitating opportunities for interventions to mitigate its severity or circumvent its development.