Hydrogen Gas Inhalation Attenuates Acute Impulse Noise Trauma: A Preclinical In Vivo Study.
衝撃性騒音外傷に対する水素ガス吸入の保護効果：前臨床動物実験
Abstract
This preclinical study examined whether hydrogen gas inhalation administered immediately after impulse noise exposure could reduce cochlear damage in guinea pigs (n=26). Animals were exposed to 400 impulse noise stimuli at 156 dB SPL, followed or not by H2 inhalation at 2 mol% (500 ml/min for 1 hour). Auditory brainstem response (ABR) thresholds were measured at five frequencies (3.15–30.0 kHz) before and 4 days after exposure, and cochleae were harvested for hair cell quantification. ABR threshold elevations were significantly smaller in the noise-plus-hydrogen group compared with the noise-only group across all tested frequencies. Outer hair cell loss in the mid-cochlear region was 53% in the noise-only group versus 22% in the hydrogen group, and inner hair cell loss was similarly reduced. Statistically significant differences were observed in the basal region for outer hair cells and in both apical and basal regions for inner hair cells, supporting a protective role of H2 inhalation against acute acoustic cochlear injury.
Mechanism
H2 inhalation is thought to scavenge reactive oxygen species generated by acute impulse noise exposure, thereby reducing oxidative damage to cochlear hair cells and limiting auditory threshold shifts.
Bibliographic
- Authors
- Videhult Pierre P, Fransson AE, Kisiel MA, Laurell GFE
- Journal
- Ann Otol Rhinol Laryngol
- Year
- 2023
- PMID
- 35962590
- DOI
- 10.1177/00034894221118764
- PMC
- PMC10315859
Tags
Delivery context
In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.
Safety notes
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