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

Abstract

Background: 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. Objectives: 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. Methods: 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. Results: 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). Conclusions: 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.

Hydrogen Gas Inhalation Attenuates Acute Impulse Noise Trauma: A Preclinical In Vivo Study

“…Fransson et al 28 found less ABR threshold shifts, OHC loss, and damage to IHC synaptic structures from 2-hour noise exposure at 115 dB SPL when immediately followed by the same H 2 treatment as in the study presented here. Bagheri et al 29 found less ABR threshold shifts from 6-hour noise exposure at 105 dB SPL per day for 5 days in combination with the asphyxiant carbon monoxide when immediately followed by exposure with gaseous H 2 (2%) 5 hours per day for 5 days. Similar to those results, 27 - 29 acoustic trauma was not fully prevented in the present study.…”

“…Bagheri et al 29 found less ABR threshold shifts from 6-hour noise exposure at 105 dB SPL per day for 5 days in combination with the asphyxiant carbon monoxide when immediately followed by exposure with gaseous H 2 (2%) 5 hours per day for 5 days. Similar to those results, 27 - 29 acoustic trauma was not fully prevented in the present study. In particular, OHC loss was unsatisfactorily high despite prompt H 2 treatment.…”

“…The present study shows that acoustic trauma from impulse noise can be reduced by prompt H 2 inhalation. To the best of our knowledge, there are 3 previous studies on H 2 inhalation and noise, 27 - 29 and one of them was performed by our group. 28 In all 3, gaseous H 2 was administered after continuous noise exposure in guinea pigs.…”