# Hydrogen Gas Inhalation Treatment in Acute Cerebral Infarction: A Randomized Controlled Clinical Study on Safety and Neuroprotection.
> 急性脳梗塞に対する水素ガス吸入の安全性と神経保護効果：無作為化対照臨床試験


## Abstract

This randomized controlled clinical trial enrolled 50 patients with acute cerebral infarction of mild-to-moderate severity (NIHSS scores 2–6) within a 6–24 hour therapeutic window. Twenty-five patients inhaled 3% H2 gas for one hour twice daily over 7 days, while 25 controls received standard intravenous medications. Assessments included daily vital signs, weekly blood chemistry, NIHSS scores, Barthel Index, and brain MRI over a 2-week period. No significant adverse events were observed in the H2 group, and oxygen saturation improved. Compared with controls, the H2 group demonstrated significant improvements in MRI relative signal intensity at the infarction site, NIHSS scores, and physical therapy outcomes as measured by the Barthel Index. These findings indicate that 3% H2 gas inhalation is both safe and associated with neurological benefit in the acute phase of cerebral infarction.

### Mechanism

H2 gas is proposed to exert antioxidant effects by selectively neutralizing reactive oxygen species at the infarction site, thereby reducing oxidative damage to neural tissue and limiting infarct progression.

## Bibliographic

- **Authors**: Ono H, Nishijima Y, Ohta S, Sakamoto M, Kinone K, Horikosi T, et al.
- **Journal**: J Stroke Cerebrovasc Dis
- **Year**: 2017
- **PMID**: [28669654](https://pubmed.ncbi.nlm.nih.gov/28669654/)
- **DOI**: [10.1016/j.jstrokecerebrovasdis.2017.06.012](https://doi.org/10.1016/j.jstrokecerebrovasdis.2017.06.012)
- **Study type**: human randomized controlled trial
- **Delivery route**: inhalation
- **Effect reported**: positive
- **H2 concentration**: 3%

## Delivery context

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

## Safety notes

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [LFL / UFL terminology](https://h2-papers.org/en/safety-notes/lfl-ufl-explained)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 28669654. https://h2-papers.org/en/papers/28669654
> **Source**: PubMed PMID [28669654](https://pubmed.ncbi.nlm.nih.gov/28669654/)