# Hydrogen Gas Inhalation Regressed Coronary Artery Aneurysm in Kawasaki Disease-Case Report and Article Review.
> 川崎病に伴う冠動脈瘤への水素ガス吸入の影響：症例報告と文献レビュー


## Abstract

Kawasaki disease (KD) is a systemic vasculitis predominantly affecting children under 5 years of age and represents a leading cause of acquired cardiac complications in developed nations, especially across Asia. This case describes a 10-year-old patient diagnosed with incomplete KD on day 12 of illness, presenting with a right coronary artery aneurysm measuring 6.08 mm in diameter and 35 mm in length. Following intravenous immunoglobulin administration, the patient's family initiated home-based hydrogen gas inhalation (77% H2, 23% O2) via nasal cannula for 1 hour daily. At the 4-month follow-up (day 138), complete regression of the aneurysm was documented, with all laboratory parameters—including complete blood count, electrolytes, liver enzymes, and renal function—remaining within normal limits. No adverse events were observed. The authors propose that hydrogen's free radical-scavenging and antioxidant properties may have contributed to aneurysm resolution, while emphasizing the need for further controlled investigation.

### Mechanism

Hydrogen gas is proposed to selectively neutralize reactive oxygen species, particularly hydroxyl radicals, thereby reducing vascular inflammation and potentially facilitating regression of coronary artery aneurysms in Kawasaki disease.

## Bibliographic

- **Authors**: Kuo HC
- **Journal**: Front Cardiovasc Med
- **Year**: 2022
- **PMID**: [35647081](https://pubmed.ncbi.nlm.nih.gov/35647081/)
- **DOI**: [10.3389/fcvm.2022.895627](https://doi.org/10.3389/fcvm.2022.895627)
- **PMC**: [PMC9133422](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9133422/)
- **Study type**: human case report
- **Delivery route**: inhalation
- **Effect reported**: positive
- **H2 concentration**: 77%

## 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 35647081. https://h2-papers.org/en/papers/35647081
> **Source**: PubMed PMID [35647081](https://pubmed.ncbi.nlm.nih.gov/35647081/)