November 2002

New Study Finds Hyperbaric Oxygen Treatments May Reduce Cognitive Problems after Carbon Monoxide Poisoning

Carbon monoxide is the leading cause of fatal poisonings in the United States, and a particular risk to fire fighters. In addition to its immediate health hazards, carbon monoxide poisoning is commonly followed by a neurologic syndrome, which may include difficulties with memory, emotions, concentration or thought. However, a recent study published in the New England Journal of Medicine (October 3, 2002) found evidence that patients who received a series of three treatments in a hyperbaric-oxygen chamber shortly after exposure were less likely to develop subsequent cognitive problems. Hyperbaric-oxygen chambers are devices that allow patients to breathe 100 percent oxygen at greater than normal atmospheric pressure.

For the study, emergency departments in Utah, Idaho, and Wyoming referred 98 percent of all patients diagnosed with carbon monoxide poisoning to LDS Hospital in Salt Lake City from 1992 to 1999. Of the 460 patients referred, 332 met the eligibility criteria for the study, and 152 agreed to participate. The participants were randomly assigned to one of two groups. Both groups had three sessions in a hyperbaric-oxygen chamber, but for half of the subjects the hyperbaric pressure was applied (the "treatment" group), while the other half spent the same amount of time in the chamber without any increased pressure (the "control" group). Neither the patients nor the study staff were told whether sessions in the chamber were with hyperbaric or normal pressure oxygen.

For all patients in the study, the first session was started within 24 hours after the end of the carbon monoxide exposure. For the subjects receiving the hyperbaric-oxygen treatment, the first chamber session consisted of 60 minutes at 3 atmospheres (304 kPa), followed by 60 minutes at 2 atmospheres (203 kPa). The second and third hyperbaric sessions consisted of 100 minutes at a pressure of 2 atmospheres. The three chamber sessions were spaced at intervals of 6 to 12 hours, and were completed in a 24-hour period.

When the patients were tested 6 weeks after treatment, 46 percent (35 out of 76) of those given normal pressure oxygen were found to have cognitive problems, compared to only 25 percent (19 out of 76) of those given hyperbaric-oxygen (P=0.007). Although patients in both groups got better over time, cognitive difficulties were still less frequent in the hyperbaric-oxygen group when they were tested again one year after treatment (P=0.04). The researchers concluded that hyperbaric-oxygen therapy may reduce the risk of cognitive difficulties following carbon monoxide poisoning.

Reference:

Weaver LK et al. Hyperbaric oxygen for acute carbon monoxide poisoning. New England Journal of Medicine 2002; Vol. 347, No. 14:1057-67.

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