# Molecular Hydrogen Reduces the Degree of Endothelial Alteration under Conditions of Chronic Heart Failure.
> 慢性心不全モデルラットにおける分子状水素吸入が循環内皮細胞数および心筋構造に及ぼす影響


## Abstract

Using a rat model of chronic heart failure, this study examined how 2% H2 gas inhalation—administered either once (40 min) or repeatedly (40 min/day for 5 consecutive days)—affected the number of circulating endothelial cells and the macrohistological architecture of cardiac tissue. Both inhalation regimens led to a reduction in circulating endothelial cell counts, with the most pronounced decline observed in the repeated-inhalation group at day 14 post-modeling. This reduction was accompanied by partial restoration of myocardial structure and a decrease in heart weight. The findings suggest that H2 inhalation limits endothelial cell damage and supports structural recovery of the myocardium under chronic heart failure conditions.

### Mechanism

Inhalation of 2% H2 reduced the number of circulating endothelial cells, indicating attenuation of endothelial injury, and was associated with structural restoration of myocardial tissue and reduced cardiac weight in heart failure rats.

## Bibliographic

- **Authors**: Deryugina AV, Danilova DA
- **Journal**: Bull Exp Biol Med
- **Year**: 2023
- **PMID**: [37773571](https://pubmed.ncbi.nlm.nih.gov/37773571/)
- **DOI**: [10.1007/s10517-023-05880-5](https://doi.org/10.1007/s10517-023-05880-5)
- **Study type**: animal study
- **Delivery route**: inhalation
- **Effect reported**: positive
- **H2 concentration**: 2%

## 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 37773571. https://h2-papers.org/en/papers/37773571
> **Source**: PubMed PMID [37773571](https://pubmed.ncbi.nlm.nih.gov/37773571/)