Twenty-six non-comatose patients with acute carbon monoxide (GO) poiso
ning were randomized into two groups. Both groups were treated as soon
as possible and for 2 h, the first group by 100% normobaric oxygen (N
BO) and the second by 100% hyperbaric oxygen. At the end of this perio
d, patients treated by HBO had a significant improvement of their clin
ical and biological conditions compared with patients treated with MBO
. Both groups then received the same NBO therapy for 10 h. At the end
of this second period, carboxyhemoglobin level was normal in both grou
ps. However, patients treated with NBO showed some clinical impairment
s, and 3 wk after onset had significantly more electroencephalogram ab
normalities and a reduced cerebral blood flow reactivity to acetazolam
ide. We conclude that HBO reduces the time of initial recovery and the
number of delayed functional abnormalities in non-comatose patients w
ith acute CO poisoning. A practical scheme for the use of NBO and HBO
in such patients is proposed.