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
- DOI
- 10.4187/respcare.12371
- PMC
- PMC12171703
Tags
Delivery context
In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.
Safety notes
See also: