The effect of hydrogen inhalation on temporary threshold shift following simultaneous exposure to noise and carbon monoxide in guinea pigs
Bagheri F, Pourbakht A, Raisi A, Kamali M, Faridan M. · Health Scope. 2018;7(4):e55353.
Study at a glance
Preclinical
Guinea pigs exposed simultaneously to noise and carbon monoxide.
2% hydrogen inhalation after combined noise and carbon-monoxide exposure. · 2% H₂.
Acute exposure and immediate post-exposure testing.
Post-exposure thresholds favored H₂ at 4, 8 and 16 kHz; the 2-kHz comparison was not reported as significant.
Very small animal study with immediate surrogate testing only.
What kind of evidence is this?
Preclinical
Randomized controlled guinea-pig study
Other neurological conditions
Inhaled H₂
Positive preclinical signal at selected frequencies.
Electrophysiological hearing outcomes in animals.
Methods
Guinea pigs exposed simultaneously to noise and carbon monoxide.
12 animals; two groups.
Acute exposure and immediate post-exposure testing.
2% hydrogen inhalation after combined noise and carbon-monoxide exposure.
Inhaled H₂-containing gas.
2% H₂.
Exposure-system flow is reported in the full methods.
Carrier-gas conditions were checked in the article.
Noise-plus-carbon-monoxide exposure without H₂.
Outcomes and reported result
Auditory brainstem response thresholds at 2, 4, 8 and 16 kHz.
Post-exposure thresholds favored H₂ at 4, 8 and 16 kHz; the 2-kHz comparison was not reported as significant.
The full article methods, intervention, outcomes, positive and null findings, funding and conflict statements were checked.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Very small animal study with immediate surrogate testing only.
The reported acute combined-exposure model only.
SYRCLE animal-study tool — preliminary
Some concerns
Random division was stated, but concealment and blinded threshold assessment were not established.
Sequence generation checked where reported · Allocation concealment generally unclear · Personnel blinding generally unclear · Outcome-assessor blinding generally unclear · No prospectively registered analysis plan identified
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
DOI: 10.5812/jhealthscope.55353 · DOI: 10.5812/jhealthscope.55353
A free publisher or repository full article was checked.
Publisher or repository full article and bibliographic record; checked 10 August 2026.
10 August 2026
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