H₂ Papers

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Protective effects of hydrogen gas inhalation on radiation-induced bone marrow damage in cancer patients: a retrospective observational study.

がん患者における放射線誘発性骨髄障害に対する水素ガス吸入の保護効果：後ろ向き観察研究

human observational study inhalation positive 5%

Abstract

This retrospective observational study investigated whether 5% H2 gas inhalation for 30 minutes following each session of intensity-modulated radiation therapy (IMRT) could reduce bone marrow damage in cancer patients. Patients in the control group (n=7) received mild hyperbaric oxygen after IMRT, while those in the hydrogen group (n=16) inhaled 5% H2 gas. Peripheral blood analysis showed that white blood cell and platelet counts declined significantly in the control group, whereas the hydrogen group exhibited significantly attenuated reductions in both parameters (P=0.0011 and P=0.0275, respectively). Red blood cell counts, hemoglobin, and hematocrit were unaffected in both groups. Importantly, anti-tumor efficacy of IMRT was comparable between groups, suggesting that H2 inhalation did not interfere with radiation's therapeutic action while offering hematoprotective benefits.

Mechanism

Molecular hydrogen is proposed to selectively neutralize hydroxyl radicals (·OH) and peroxynitrite (ONOO⁻) generated during radiation exposure, thereby reducing oxidative damage to bone marrow cells without impairing the ionizing effects on tumor tissue.

Bibliographic

Authors
Hirano S, Aoki Y, Li XM, Ichimaru N, Takahara S, Takefuji Y
Journal
Med Gas Res
Year
2021
PMID
33942780
DOI
10.4103/2045-9912.314329
PMC
PMC8174412

Tags

Disease:cancer radiation (side-effect) (41) Delivery:inhalation delivery (196) Mechanism:hydroxyl radical scavenging (352) anti-inflammatory (743) oxidative stress (899) peroxynitrite scavenging (64) 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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