Hyperbaric oxygen therapy and contralateral ear hearing thresholds in unilateral sudden sensorineural hearing loss

Abstract

Aim: To evaluate changes in hearing thresholds of the clinically unaffected contralateral ear before and after hyperbaric oxygen therapy (HBOT) in patients treated for unilateral idiopathic sudden sensorineural hearing loss (ISSNHL).

Materials and Methods: In this single-center retrospective observational study, pure-tone audiograms (250 Hz–8 kHz) of the contralateral ears of 101 patients who underwent HBOT were compared before and after treatment. Each session lasted approximately 120 minutes at 2.4 ATA, including compression, oxygen exposure, and decompression phases. Thresholds were age-corrected according to ISO 7029:2017. Depending on distributional assumptions, Wilcoxon signed-rank test were used for paired comparisons (α=0.05). The median number of sessions was 20 (IQR: 10–20).

Results: No significant changes were observed across most frequencies. Only at 6000 Hz, a minimal but statistically significant difference was detected (p=0.0049). The hearing thresholds at other frequencies remained stable.

Conclusion: Overall, HBOT was not associated with substantial changes in contralateral hearing thresholds. The minor threshold shift observed at 6 kHz may suggest noise exposure during treatment sessions rather than oxidative stress. This highlights the importance of monitoring high-frequency hearing and emphasizes the need for noise control measures during therapy. These findings confirm that HBOT is generally safe for the unaffected ear.