The goal of this observational study is to measure the effect of hyperbaric oxygen therapy on middle ear pressure in order to predict the risk factors for middle ear barotrauma also, to assess its effects on hearing functions of the inner ear in participant population. The main questions aim to answer are:

• Is there a change in middle ear pressure before and after exposure to hyperbaric oxygen therapy ?
• Is there a change in hearing threshold level before and after exposure to hyperbaric oxygen therapy ? The middle ear pressure, eustachian tube functions and the hearing threshold of the participants will be assessed immediately before the fist session and within one hour after the first and tenth sessions.

Fifty four patients already treated by hyperbaric oxygen therapy recruited from hyperbaric oxygen therapy center of Assiut university hospitals. Otoscopic examination for all patients must be done before and after the session , assessment of middle ear pressure and the state of the eustachian tube through doing eustachian tube function tests (Valsalva and Toynbee tests for ears with intact tympanic membrane and modified inflation - deflation tests for ears with perforated tympanic membrane) by tympanometry for all patients before and after the first session of hjyperbaric oxygen therapy and after completion of the tenth session. Assessment of the hearing threshold level of the patients immediately before the first session and after the tenth session of hyperbaric oxygen therapy through doing pure tone audiometry ( air conduction and bone conduction audiometry) and speech audiometry to assess the speech discrimination score for the patients

Inclusion Criteria:

• Patients of at least 18 years old.
• Patients accept participation in the research.
• Patients with out history of middle ear diseases.

Exclusion Criteria:

• Patients under age of 18 years old.
• Patients have middle ear effusion.
• Patients refuse to participate in the research.

Patients of both sexes already recommended to be treated by hyperbaric oxygen therapy for various medical conditions in hyperbaric oxygen therapy center.