Effect of hydrogen/oxygen therapy for ordinary COVID-19 patients: a propensity-score matched case-control study
Zeng Y, Guan W, Wang K, Jie Z, Zou X, Tan X, Li X, Chen X, Ren X, Jiang J, Zheng Z, Shi J, Zhong N. · BMC Infectious Diseases. 2023;23:440.
Study at a glance
Human
Adults hospitalized in China with ordinary, non-severe COVID-19 between December 2019 and March 2020.
Nasal-mask H₂/O₂ for at least six hours daily on more than seven consecutive days, plus standard care. · Total mixture flow was 3.0 L/min; direct 2:1 calculation gives H₂ flow 2.0 L/min and O₂ flow 1.0 L/min.
At least six hours/day for more than seven consecutive days; clinical follow-up through discharge and day-28 discharge-rate analysis.
Matched median stay was 12 versus 13 days and later discharge rates and day-5 SpO₂ favored H₂/O₂. Day-14 discharge did not differ significantly. Gender and time from symptom onset were not associated with stay within the H₂/O₂ subgroup; no significant adverse effects were observed.
Retrospective nonrandomized study with small matched groups, propensity matching on only age, sex and time to admission, possible unmeasured confounding, incomplete post-treatment laboratory/SpO₂ data and early-pandemic care. Public Chinese grants were reported and authors declared no competing interests.
What kind of evidence is this?
Human
Three-centre retrospective propensity-score-matched case-control study
Respiratory health
Inhaled H₂
Information not yet classified
Some editorial classification fields are still pending. The source-reported outcomes and result are shown below; Hydrogenology does not infer a positive or negative signal from prose automatically.
Methods
Adults hospitalized in China with ordinary, non-severe COVID-19 between December 2019 and March 2020.
180 eligible records before matching: 42 H₂/O₂ and 138 oxygen. The principal 1:2 matched analysis included 33 H₂/O₂ and 55 oxygen patients.
At least six hours/day for more than seven consecutive days; clinical follow-up through discharge and day-28 discharge-rate analysis.
Nasal-mask H₂/O₂ for at least six hours daily on more than seven consecutive days, plus standard care.
Brown's gas / oxyhydrogen at an H₂:O₂ volume ratio of 2:1.
Total mixture flow was 3.0 L/min; direct 2:1 calculation gives H₂ flow 2.0 L/min and O₂ flow 1.0 L/min.
2,000 mL/min.
1,000 mL/min.
Standard care plus low-flow air/oxygen therapy below 3.0 L/min, with duration adjusted clinically.
Outcomes and reported result
Hospital length of stay, discharge by days 14, 21 and 28, day-5 SpO₂, vital signs, respiratory symptoms, adverse events and mortality.
Matched median stay was 12 versus 13 days and later discharge rates and day-5 SpO₂ favored H₂/O₂. Day-14 discharge did not differ significantly. Gender and time from symptom onset were not associated with stay within the H₂/O₂ subgroup; no significant adverse effects were observed.
The complete free PMC article and supplementary-analysis descriptions were checked for the unmatched and matched cohorts, gas ratio/flow, schedule, primary and null results, safety, funding and conflicts.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Retrospective nonrandomized study with small matched groups, propensity matching on only age, sex and time to admission, possible unmeasured confounding, incomplete post-treatment laboratory/SpO₂ data and early-pandemic care. Public Chinese grants were reported and authors declared no competing interests.
Ordinary COVID-19 hospitalized during the original 2019–2020 outbreak; contemporary treatment relevance is uncertain.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 37386364 · DOI: 10.1186/s12879-023-08424-4
Free full article in PubMed Central.
Complete PMC article, supplementary-analysis descriptions and PubMed metadata; full-text extraction checked 9 August 2026.
10 August 2026
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