H(2) gas improves functional outcome after cardiac arrest to an extent comparable to therapeutic hypothermia in a rat model.
ラットモデルにおける心停止後症候群に対する水素ガス吸入の効果：治療的低体温法との比較
Abstract
Using a rat ventricular fibrillation model, this study examined the effects of 2% H2 gas inhalation initiated at the start of cardiopulmonary resuscitation on post-cardiac arrest syndrome. Four groups were compared: normothermia with N2, normothermia with H2, therapeutic hypothermia (TH, 33°C) with N2, and TH with H2. Gas mixtures and TH were maintained for 2 hours after return of spontaneous circulation. H2 inhalation improved survival rates and neurological deficit scores to a degree comparable to TH. Unlike TH, H2 inhalation also prevented increases in left ventricular end-diastolic pressure and serum IL-6 levels. Marked reductions in 8-OHdG- and 4-HNE-positive cardiomyocytes indicated that hydroxyl radical scavenging contributed substantially to these protective effects. Combined H2 inhalation and TH did not produce additive benefits beyond either intervention alone.
Mechanism
H2 gas scavenges hydroxyl radicals, thereby reducing oxidative DNA damage (8-OHdG) and lipid peroxidation (4-HNE) in cardiomyocytes and attenuating ischemia-reperfusion injury following cardiac arrest.
Bibliographic
- Authors
- Hayashida K, Sano M, Kamimura N, Yokota T, Suzuki M, Maekawa Y, et al.
- Journal
- J Am Heart Assoc
- Year
- 2012
- PMID
- 23316300
- DOI
- 10.1161/JAHA.112.003459
- PMC
- PMC3541633
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: