# Performance of Unmodified Mechanical Ventilators With 2% Hydrogen Gas Mixtures.
> 2%水素ガス混合気体を用いた未改造人工呼吸器の性能評価


## Abstract

This experimental study assessed whether four unmodified mechanical ventilators could accurately deliver 2% H2 gas mixtures across neonatal-to-adult ventilator settings using a closed test circuit. The Maquet Servo-i, Servo-u, and Dräger Evita Infinity V500 all demonstrated tidal volume and FiO2 delivery within ±10% bias compared with set values, and each passed pre-use safety checks. In contrast, the Dräger Babylog VN500 showed a mean tidal volume bias of −89.2% (95% CI −107.0 to −71.3), attributed to its hot-wire anemometry flow sensor and elevated operating temperature, which are incompatible with the physical properties of H2. These findings suggest that certain adult and pediatric ventilators can administer 2% H2 mixtures without hardware modification, whereas neonatal devices employing hot-wire sensors may require alternative approaches.

### Mechanism

H2 gas possesses antioxidant, anti-inflammatory, and anti-apoptotic properties relevant to ischemia-reperfusion injury. This study examined device compatibility for clinical H2 delivery rather than biological mechanisms directly.

## Bibliographic

- **Authors**: Mancebo JG, Sack K, Nguyen R, Peng Y, Sosa S, Anders M, et al.
- **Journal**: Respir Care
- **Year**: 2025
- **PMID**: [39969918](https://pubmed.ncbi.nlm.nih.gov/39969918/)
- **DOI**: [10.4187/respcare.12371](https://doi.org/10.4187/respcare.12371)
- **PMC**: [PMC12171703](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12171703/)
- **Study type**: other
- **Delivery route**: inhalation
- **Effect reported**: not assessed
- **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 39969918. https://h2-papers.org/en/papers/39969918
> **Source**: PubMed PMID [39969918](https://pubmed.ncbi.nlm.nih.gov/39969918/)