Hydrogen inhalation during normoxic resuscitation improves neurological outcome in a rat model of cardiac arrest independently of targeted temperature management.
心停止ラットモデルにおける常酸素条件下の蘇生時水素吸入が標的体温管理とは独立して神経学的転帰を改善する
Abstract
This study investigated the efficacy of 1.3% H2 inhalation initiated after return of spontaneous circulation (ROSC) under normoxic conditions in a rat ventricular fibrillation cardiac arrest model. Following 6 minutes of cardiac arrest and cardiopulmonary resuscitation, animals were randomized 5 minutes post-ROSC into four groups: normothermia control (26% O2), H2 inhalation (26% O2 + 1.3% H2), targeted temperature management (TTM), and combined TTM plus H2. Seven-day survival rates were 38.4% (control), 71.4% (H2 and TTM groups), and 85.7% (TTM+H2). Neurological deficit scores at 24, 48, and 72 hours post-ROSC and motor activity at 7 days were superior in the combined group compared with TTM alone. Neuronal degeneration and microglial activation in vulnerable brain regions were suppressed by both individual interventions, with the combination yielding the greatest effect. H2 inhalation provided benefit even without hyperoxic conditions.
Mechanism
H2 inhalation suppresses neuronal degeneration and microglial activation in vulnerable brain regions following cardiac arrest; combined with targeted temperature management, these neuroprotective effects are further enhanced.
Bibliographic
- Authors
- Hayashida K, Sano M, Kamimura N, Yokota T, Suzuki M, Ohta S, et al.
- Journal
- Circulation
- Year
- 2014 (2014-12-09)
- PMID
- 25366995
- DOI
- 10.1161/CIRCULATIONAHA.114.011848
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
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