Hearing Function in Obstructive Sleep Apnoea (OSA) patients and its impact with Continuous Positive Airway Pressure (CPAP)

Abstract

Background: The relationship between obstructive sleep apnoea (OSA) and hearing dysfunction has not been comprehensively evaluated. The obstruction of the upper airway in OSA could lead to anatomical changes to the eustachian tube, thus impacting middle ear function. In addition, the recurrent decrease in oxygen saturation during sleep with OSA could have potential impacts on cochlear and central auditory function. The treatment for OSA is continuous positive airway pressure (CPAP), a device that splints the airway with positive pressure. The positive pressure could potentially aerate the eustachian tube and thereby alter middle ear function. Aim: To comprehensively evaluate peripheral hearing function through a battery of audiological assessments in patients with OSA and its impact on CPAP treatment. Methods: An observational study of 91 patients (15 no OSA, 31 mild OSA, 14 moderate OSA and 31 severe OSA) with hearing assessments in the sleep laboratory. This study was separated into three parts: to investigate hearing function in patients with OSA before sleep; the change in middle ear function during sleep; and the impact CPAP has on hearing function in patients with OSA. Results: Increasing OSA severities was associated with reduced cochlear outer hair cell function through otoacoustic emissions. This is likely related to hypoxia and not a conductive hearing loss through middle ear disorder. During sleep, middle ear pressure (MEP) increased in all patients, regardless of OSA severities. The increase in MEP was not associated with oxygen saturation. Cochlear hair cell function and hearing thresholds were not impacted after sleep in patients with OSA. CPAP treatment increased MEP during overnight use in patients with OSA. The increase in MEP was proportional to the increase in CPAP pressure. CPAP did not appear to have an impact on other auditory regions. Conclusions: Patients with OSA have worse outer cochlear hair cell function. The treatment of CPAP increases MEP only. Further research is required to investigate other mechanisms relating OSA to hearing dysfunction, eg, focusing on changes in blood flow and the importance of CO₂ on middle ear mucosal gas exchange. The impact of OSA on central auditory regions will need to be examined.