Effects of breathing mixed gas with oxygen in different concentrations on delayed otic barotrauma

Objective 　To investigate the delayed changes in middle ear function and audition after rapid changes in ambient pressure while breathing mixed gas with oxygen in different concentrations. Methods 　Five healthy male subjects, sitting in the hypobaric chamber breathed pure oxygen, 60% oxygen-rich air, or air respectively, one hour before hypobaric chamber test. The interval of two tests was longer than two weeks. After 20m/s rapid changes in the ambient pressure, all the three groups were tested with subjective symptoms, degree of congestion, middle ear function and audition at four timing. Results 　Just after test, the amount of symptomatic ears were 8, 2 and 3 in pure oxygen group, 60% oxygen-rich air group and air group, respectively. Some subjects in pure oxygen group felt aural fullness and pain again 3 hours after tests. The amount of Ⅲ°congestion ears was 5, 2 and 3 in each group respectively with no congestion aggravation. The amount of ears with A type tympanogram was 5, 6 and 6 in each group respectively. The extraction ratio of tympanogram and acoustic reflex incomplete in all groups recovered gradually to the initial value without obviously delayed data rebound. The middle ear pressure and pure-tone threshold in subjects of pure oxygen group changed more obviously and recovered more slowly. Conclusion 　In hypobaric chamber test, the incidence of otic barotrauma may increase in those subjects breathing pure oxygen with symptoms aggravation and repetition within 24h. DOI: 10.11855/j.issn.0577-7402.2016.04.14