Hyperbaric hydrogen therapy improves secondary brain injury after head trauma.
高圧水素吸入による外傷性脳損傷後の二次性脳障害への影響：マウスモデルを用いた検討
Abstract
Secondary brain injury following traumatic brain injury (TBI) involves biochemical cascades driven largely by oxidative stress, making molecular hydrogen a candidate intervention. In this mouse study, 120 animals were allocated to three groups: TBI without intervention, TBI with hyperbaric hydrogen (HBH2) at 2 atmospheres for 90 minutes beginning 30 minutes post-injury, and a sham group. Moderate cerebral contusion was induced via controlled cortical impact. Compared with the untreated TBI group, the HBH2 group exhibited significantly reduced cerebral edema, a greater number of surviving hippocampal neurons at day 28, and markedly lower hyperactivity scores at day 14. These findings suggest that elevating hydrogen partial pressure through hyperbaric conditions enhances neuroprotective efficacy beyond what atmospheric-pressure delivery can achieve.
Mechanism
Increasing ambient pressure raises hydrogen partial pressure, enabling greater reactive oxygen species scavenging that attenuates oxidative-stress-driven secondary injury, thereby reducing cerebral edema and preserving hippocampal neurons.
Bibliographic
- Authors
- Otsuka Y, Tomura S, Toyooka T, Takeuchi S, Tomiyama A, Omura T, et al.
- Journal
- Undersea Hyperb Med
- Year
- 2023
- PMID
- 38055881
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
See also: