# Molecular Hydrogen Positively Affects Physical and Respiratory Function in Acute Post-COVID-19 Patients: A New Perspective in Rehabilitation.
> 急性COVID-19後患者における分子状水素吸入が身体機能および呼吸機能に与える影響：リハビリテーションへの新たな視点


## Abstract

A randomized, single-blind, placebo-controlled trial enrolled 50 acute post-COVID-19 patients (26 males aged 44±17 years; 24 females aged 38±12 years) who were symptomatic between 21 and 33 days after a positive PCR test. Participants underwent hydrogen gas or placebo inhalation twice daily for 60 minutes over 14 days. Outcomes included the 6-minute walk test (6MWT), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1). Compared with placebo, hydrogen inhalation produced statistically significant improvements: 6MWT distance increased by 64±39 m, FVC by 0.19±0.24 L, and FEV1 by 0.11±0.28 L (all p≤0.025). These findings indicate that hydrogen gas inhalation may facilitate early restoration of physical and respiratory capacity in this patient population.

### Mechanism

Molecular hydrogen is proposed to exert antioxidative, anti-inflammatory, anti-apoptotic, and antifatigue effects, thereby reducing oxidative stress and systemic inflammation associated with post-COVID-19 sequelae and supporting recovery of physical and pulmonary function.

## Bibliographic

- **Authors**: Botek M, Krejčí J, Valenta M, McKune A, Sládečková B, Konečný P, et al.
- **Journal**: Int J Environ Res Public Health
- **Year**: 2022 (2022-02-10)
- **PMID**: [35206179](https://pubmed.ncbi.nlm.nih.gov/35206179/)
- **DOI**: [10.3390/ijerph19041992](https://doi.org/10.3390/ijerph19041992)
- **PMC**: [PMC8872486](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8872486/)
- **Study type**: human randomized controlled trial
- **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 35206179. https://h2-papers.org/en/papers/35206179
> **Source**: PubMed PMID [35206179](https://pubmed.ncbi.nlm.nih.gov/35206179/)