The Effect of Hydrogen Inhalation on Temporary Threshold Shift Following Simultaneous Exposure to Noise and Carbon Monoxide in Guinea Pigs

People might simultaneously be exposed to noise and carbon monoxide in occupational settings. The previous studies revealed that the inhalation of molecular hydrogen (H2) exerts some healing effects on multiple diseases including hearing loss. The levels of free radicals have been shown to increase due to the exposure to noise plus carbon monoxide. This study examined the possible protective effects of hydrogen inhalation following simultaneous exposure to noise and carbon monoxide in Guinea pigs. Twelve Guinea pigs were randomly divided into two different groups: (1) Exposed to noise plus carbon monoxide and (2) exposed to noise plus carbon monoxide along with the inhalation of hydrogen. Auditory brainstem responses (ABRs) at different frequencies of 2, 4, 8, and 16 kHz were measured before and immediately after the exposure. The ABR thresholds measured immediately after the simultaneous exposure to noise and carbon monoxide significantly increased at all frequencies in group 1 while in group 2, the ABR thresholds measured immediately after the inhalation of hydrogen significantly reduced at 4, 8, and 16 kHz (P values < 0.05). This finding indicates that there is a protective effect associated with the inhalation of 2% hydrogen on the development of hearing loss after the simultaneous exposure to noise and carbon monoxide and this effect was fairly significant at higher frequencies.