Does delayed hyperbaric oxygen therapy improve neurological outcome in carbon monoxide toxicity?

April 2, 2011, 10:01 pm


Factors affecting the prognosis of patients with delayed encephalopathy after acute carbon monoxide poisoning. Hu H et al. Am J Emerg Med 2011 March;29:261-264.


The goal of treating acute carbon monoxide (CO) toxicity with hyperbaric oxygen (HBO) is to prevent delayed neurological sequelae which can occur days or weeks after exposure and follow a period of time during which the patient is lucid and has apparently recovered from the acute poisoning.  There is still controversy as to whether treatment with HBO in the acute phase can decrease incidence of delayed sequelae and, if so, in what patients.

This paper does not address the possible effectiveness of HBO in acute CO toxicity. Rather, it asks if treatment after delayed sequelae have occurred can improve prognosis.  Unfortunately, it utterly fails to answer this question.

This is not surprising, given the clueless study design.  The investigators looked retrospectively at 46 patients with delayed encephalopathy after acute carbon monoxide poisoning.  All were treated with HBO. Let me repeat that: All were treated with HBO. There was no control group — no even historic controls.  It is obvious on the face that this design makes it impossible to determine what effect — if any — the HBO treatment had.  And by the way, when the authors say “treated”, they mean “treated“. The patients underwent between 24 and 82 one-hour HBO treatments each.

I won’t even bother going through the authors conclusions, since they are not in any way supported by the study.  Those interested can refer to the abstract or the paper.  The only relevant factoid I got from their data was that despite treatment with HBO during the acute phase of CO toxicity, 33 of their patients went on to develop delayed neurological sequelae.

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