© 2008 American Thoracic Society
CO Poisoning and Hyperbaric Oxygen Therapy: More Studies Need to Be DoneTo the Editor:We read with interest the article by Dr. Weaver and colleagues, and we don't believe that their conclusions are founded on data that would cause a change in the standard of care for the treatment of carbon monoxide–poisoned patients (1). Their study combined patients enrolled in a previously reported randomized controlled trial (RCT) (2) with patients who did not participate in that RCT. The 91 patients in the latter group had not been enrolled in the RCT for various reasons, including refusal to participate and presenting too late after CO exposure. Did these 91 patients represent every single patient excluded from initial randomization? Were provisions for repeated neuropsychiatric testing and data collection despite exclusion from randomization approved in the original protocol by the institutional review board? Was an incentive offered for participation, and was this incentive the same as that for subjects enrolled in the original RCT? The authors advise hyperbaric oxygen (HBO) therapy for symptomatic CO-poisoned patients aged 36 years and older. However, combining the two patient groups represents post hoc analyses (acknowledged by the authors) of a nonrandomized trial, or quasi-experimental design. Hence, results cannot represent evidence any stronger than those from an observational study with inherent biases and both known and unknown confounders. Was the cutoff of 36 years chosen a priori or was it chosen post hoc during statistical analyses? The authors wrote that "If the patient complained of memory, attention, or concentration difficulties, the required neuropsychological test decrement was decreased to greater than one standard deviation below the mean of demographically corrected standardized T scores on any one subtest." Using such a liberal cutoff increases the sensitivity at the expense of specificity. As the authors recognized, subjective complaints such as poor memory and concentration can result from causes other than CO poisoning. We noticed no mention of alcoholism, alcohol intoxication, or secondary gain issues, such as litigation. Were these considered or adjusted for? In summary, the conclusion that HBO should be recommended to patients aged 36 years or older is hypothesis-generating, at best. We believe physicians should adhere to the American College of Emergency Physicians guideline that was based on a review of the RCT by Weaver and colleagues (2) as well as the other evidence. The guideline states that HBO is a therapeutic option for CO-poisoned patients, but its use cannot be mandated, and that no clinical variables identify a subgroup of CO-poisoned patients for whom HBO is most likely to provide benefit or cause harm (3).
Banner Good Samaritan Regional Medical Center FOOTNOTES Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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