# Hydrogen gas reduces chronic intermittent hypoxia-induced hypertension by inhibiting sympathetic nerve activity and increasing vasodilator responses via the antioxidation.
> 水素ガス吸入による慢性間欠的低酸素誘発性高血圧の抑制：交感神経活動と血管拡張応答への影響


## Abstract

Using a rat model of chronic intermittent hypoxia (CIH) achieved by 8 hours/day exposure over 5 weeks, the effects of H2 gas inhalation (2 hours/day) on cardiovascular parameters were examined. CIH elevated both systolic and diastolic blood pressure, increased renal sympathetic nerve activity, and raised plasma norepinephrine levels. Co-administration of H2 gas markedly reduced these blood pressure elevations and restored abnormal vascular relaxation responses. Oxidative stress markers showed improvement: 8-hydroxy-2-deoxyguanosine content declined while superoxide dismutase activity increased in H2-treated CIH rats. H2 inhalation alone produced no significant cardiovascular changes. The findings suggest that antioxidant activity of H2 underlies suppression of sympathetic nerve activity and reduction of systemic vascular resistance, collectively contributing to blood pressure normalization in CIH-exposed animals.

### Mechanism

H2 exerts antioxidant effects—evidenced by increased superoxide dismutase activity and decreased 8-hydroxy-2-deoxyguanosine—which suppress renal sympathetic nerve activity and reduce systemic vascular resistance, thereby attenuating CIH-induced blood pressure elevation.

## Bibliographic

- **Authors**: Guan P, Lin XM, Yang SC, Guo Y, Li W, Zhao Y, et al.
- **Journal**: J Cell Biochem
- **Year**: 2019
- **PMID**: [30259991](https://pubmed.ncbi.nlm.nih.gov/30259991/)
- **DOI**: [10.1002/jcb.27684](https://doi.org/10.1002/jcb.27684)
- **Study type**: animal study
- **Delivery route**: inhalation
- **Effect reported**: positive

## 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 30259991. https://h2-papers.org/en/papers/30259991
> **Source**: PubMed PMID [30259991](https://pubmed.ncbi.nlm.nih.gov/30259991/)