H₂ Papers

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The effect of hydrogen gas on a mouse bilateral common carotid artery occlusion.

マウス両側総頸動脈閉塞モデルにおける水素ガス吸入の効果

animal study inhalation positive 1.3%

Abstract

Male C57BL/6J mice underwent transient bilateral common carotid artery occlusion (BCCAO) using a nontraumatic aneurysm clip and were assigned to sham, BCCAO, or BCCAO plus 1.3% hydrogen gas inhalation groups. Cerebral blood flow in both cortical hemispheres was monitored continuously via laser Doppler perfusion imaging, and vital signs were recorded throughout. At 24 hours post-ischemia, oxidative stress was quantified by 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, neuronal damage in the hippocampal CA1 region was histologically assessed, and brain water content was measured. Hydrogen gas administration did not alter vital signs or cerebral blood flow. Nevertheless, 8-OHdG expression was reduced, hippocampal CA1 neuronal injury was diminished, and brain edema was attenuated in hydrogen-treated animals, suggesting a neuroprotective role for hydrogen gas in this ischemia model.

Mechanism

Hydrogen gas is proposed to selectively scavenge hydroxyl radicals, thereby reducing oxidative DNA damage (8-OHdG), attenuating hippocampal CA1 neuronal injury, and limiting cerebral edema following bilateral carotid occlusion.

Bibliographic

Authors
Nagatani K, Takeuchi S, Kobayashi H, Otani N, Wada K, Fujita M, et al.
Journal
Acta Neurochir Suppl
Year
2013
PMID
23564105
DOI
10.1007/978-3-7091-1434-6_10

Tags

Disease:cognitive decline (111) ischemia-reperfusion injury (107) Delivery:inhalation delivery (196) Mechanism:hydroxyl radical scavenging (352) anti-inflammatory (743) oxidative stress (899) reactive oxygen species (774)

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.

→ Evidence by delivery route

Safety notes

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.

See also:

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