Aims: 1. To determinate whether there is cochlear receptor cells damage in OSAS patients depending on the degree of the disease 2. Investigate whether the use of ventilation devices with continuous positive pressure and constant oxygen pressure in the airways can lead to the recovery of the cochlear receptor cells Participants and

Methods: The investigation work will be designed as original scientific research- prospective cohort study at Department od Otorhinolaryngology and Head and Neck Surgery, University Hospital Center Osijek. The participants will be divided in two groups: target group with obstructive sleep apnea (n45) and control group with healthy individuals (n32). Research plan: All participating in this study will complete the following questionnaires: STOP- BANG and Epworth drowsiness scale. Subjects of the target group with moderate or severe obstructive sleep apnea will be referred to an otorhinolaryngologist audiologist for complete examination and processing after examination by a neurologist. These participants will be examined by an audiologist after 6-8 months of continuous and adequate use of the CPAP device for reevaluation. Participants of a control group will be patients examined or treated in Department of Otorhinolaryngology and Head and Neck surgery for other diseases in whom specific questionnaires excluded the existence of obstructive sleep apnea. Audiological diagnostics will be performed on all patients on the same devices of the Department of Audiology and Phoniatrics . Expected scientific contribution: To prove the existence of receptor hearing impairment in the patients with obstructive sleep apnea; and then to prove that the use of a of continuous positive airway pressure with constant oxygen pressure in patients with OSAS using CPAP devices leads to the recovery of the cochlear receptor cells whose damage occurred as a result prolonged recurrent hypoxia. In addition, to determine the importance of a broader diagnostic processing of patients with obstructive sleep apnea.