# Gas Therapies for Neuro-Protection.
> 心停止後の神経保護を目的としたガス療法：一酸化窒素・水素・キセノン・アルゴンの可能性


## Abstract

Cardiac arrest (CA) continues to be a leading contributor to death and neurological disability worldwide, highlighting the demand for novel neuroprotective approaches. This review examines the evidence for inhaled gas agents—nitric oxide (NO), molecular hydrogen (H2), xenon (Xe), and argon (Ar)—as candidates for post-CA neuroprotection. Each gas demonstrates protective properties mediated through antioxidant activity, suppression of inflammatory cascades, and inhibition of apoptotic pathways, collectively helping to preserve neurological function following ischemic insult. Preclinical models and early-phase clinical investigations have yielded encouraging results; however, the authors emphasize that large-scale randomized trials are required to confirm efficacy, establish optimal dosing regimens, and facilitate integration into standard resuscitation protocols.

### Mechanism

The reviewed gases, including H2, are proposed to reduce post-cardiac-arrest neurological injury via antioxidant scavenging of reactive species, suppression of inflammatory signaling, and inhibition of apoptotic cell death pathways.

## Bibliographic

- **Authors**: Merigo G, Ristagno G
- **Journal**: Crit Care Clin
- **Year**: 2026
- **PMID**: [41260719](https://pubmed.ncbi.nlm.nih.gov/41260719/)
- **DOI**: [10.1016/j.ccc.2025.08.004](https://doi.org/10.1016/j.ccc.2025.08.004)
- **Study type**: review
- **Delivery route**: inhalation
- **Effect reported**: not assessed

## 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 41260719. https://h2-papers.org/en/papers/41260719
> **Source**: PubMed PMID [41260719](https://pubmed.ncbi.nlm.nih.gov/41260719/)