# Daily inhalation of hydrogen gas has a blood pressure-lowering effect in a rat model of hypertension.
> 水素ガス吸入による高血圧ラットモデルでの血圧低下効果の検討


## Abstract

Using a 5/6 nephrectomy rat model, the effects of daily 1-hour inhalation of a 1.3% hydrogen gas mixture on blood pressure were investigated. Hydrogen inhalation significantly suppressed the rise in blood pressure following nephrectomy, and the antihypertensive effect was also confirmed in rats already in a stable hypertensive state three weeks post-surgery. Continuous blood pressure monitoring via an implanted telemetry system revealed that the effect persisted during both daytime rest and nighttime activity periods. Spectral analysis of blood pressure variability indicated that hydrogen inhalation improved autonomic nervous system balance by dampening overactive sympathetic activity and enhancing parasympathetic tone, changes that coincided temporally with the observed blood pressure reduction.

### Mechanism

Hydrogen inhalation appears to lower blood pressure by suppressing excessive sympathetic nervous system activity while augmenting parasympathetic activity, thereby restoring autonomic balance as evidenced by spectral analysis of blood pressure variability.

## Bibliographic

- **Authors**: Sugai K, Tamura T, Sano M, Uemura S, Fujisawa M, Katsumata Y, et al.
- **Journal**: Sci Rep
- **Year**: 2020 (2020-11-26)
- **PMID**: [33244027](https://pubmed.ncbi.nlm.nih.gov/33244027/)
- **DOI**: [10.1038/s41598-020-77349-8](https://doi.org/10.1038/s41598-020-77349-8)
- **PMC**: [PMC7692487](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7692487/)
- **Study type**: animal study
- **Delivery route**: inhalation
- **Effect reported**: positive
- **H2 concentration**: 1.3%

## 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 33244027. https://h2-papers.org/en/papers/33244027
> **Source**: PubMed PMID [33244027](https://pubmed.ncbi.nlm.nih.gov/33244027/)