This double blind, randomised trial compared treatment of acute carbon monoxide poisoning with three sessions of either hyperbaric oxygen (100% oxygen at 3 atmospheres during the first session and then 2 atmospheres absolute in the subsequent two sessions) or normobaric oxygen (air at 1 atmosphere absolute during all three sessions). The incidence of neurological sequelae at 6 weeks was used as the primary outcome and assessment included a neurological examination, neuropsychological tests, and a questionnaire based on symptoms. Cognitive sequelae occurred in 25% of patients in the hyperbaric oxygen group compared with 46% in the normobaric oxygen group (unadjusted odds ratio 0.39; p=0.007). There was also a reduction in cognitive sequelae at 6 and 12 months in the hyperbaric oxygen group.

The study shows that hyperbaric oxygen therapy reduces the risk of neurological sequelae at 6 weeks and 12 months after acute carbon monoxide poisoning.