# Hydrogen ventilation combined with mild hypothermia improves short-term neurological outcomes in a 5-day neonatal hypoxia-ischaemia piglet model.
> 新生児低酸素虚血性脳症ブタモデルにおける水素吸入と軽度低体温の併用による短期神経学的転帰の改善


## Abstract

This animal study examined whether combining hydrogen gas inhalation with mild hypothermia could improve outcomes in a neonatal hypoxic-ischaemic encephalopathy (HIE) piglet model. Three groups were compared: normothermia, hypothermia alone (33.5 ± 0.5 °C), and hypothermia plus 2.1–2.7% H2 inhalation, each administered for 24 hours. Neurological assessments were conducted every 6 hours over 5 days post-weaning. Piglets receiving the combined intervention showed significantly higher neurological scores from day 3 onward compared with the normothermia group, and most regained walking ability by day 3. Histopathological analysis on day 5 revealed improved cortical gray matter and subcortical white matter integrity, along with a marked reduction in cell death, in the combination group. These findings suggest that H2 inhalation augments the neuroprotective effects of hypothermia in neonatal HIE.

### Mechanism

H2 inhalation is proposed to complement hypothermia-mediated neuroprotection through antioxidant, anti-inflammatory, and anti-apoptotic mechanisms, collectively reducing neuronal cell death in cortical and subcortical regions.

## Bibliographic

- **Authors**: Htun Y, Nakamura S, Nakao Y, Mitsuie T, Nakamura M, Yamato S, et al.
- **Journal**: Sci Rep
- **Year**: 2019 (2019-03-11)
- **PMID**: [30858437](https://pubmed.ncbi.nlm.nih.gov/30858437/)
- **DOI**: [10.1038/s41598-019-40674-8](https://doi.org/10.1038/s41598-019-40674-8)
- **PMC**: [PMC6411734](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6411734/)
- **Study type**: animal study
- **Delivery route**: inhalation
- **Effect reported**: positive
- **H2 concentration**: 2.1–2.7%

## 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 30858437. https://h2-papers.org/en/papers/30858437
> **Source**: PubMed PMID [30858437](https://pubmed.ncbi.nlm.nih.gov/30858437/)