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Editor,—I read with interest the article by Turner et al, providing an update on carbon monoxide poisoning.1 The authors correctly point out that hyperbaric therapy remains controversial, and that no controlled clinical trial had been conducted comparing hyperbaric oxygen (HBO) with normobaric oxygen (NBO). Since the date of acceptance of their paper a prospective, blinded, randomised trial comparing NBO with HBO has been published.2 This trial also included severely poisoned patients and incorporated sham treatments. This study found in 191 patients that three days of HBO (2.8 atmospheres for 60 minutes) offered no advantages compared with three days of NBO (100 minutes of 100%). Another study is continuing in the United States and the interim results3 have found no difference in the incidence of persistent neurological sequelae between those treated with HBO compared with NBO, although there is an increased incidence of delayed sequelae in one of the blinded treatment arms.
The authors also recommend careful neurological and cognitive re-examination. It is worth highlighting that cognitive testing in carbon monoxide poisoning is far from standardised. Many studies utilise different screening tests, different time intervals to re-screening, and different HBO regimens. This lack of standardisation makes it difficult to compare studies and no doubt contributes to our inability to provide definitive recommendations in the management of carbon monoxide poisoning.
The authors reply
We also read with interest the paper by Scheinkestel et al, which was published after acceptance of our article.1 Scheinkestel's paper was accompanied by a detailed editorial which documented a number of criticisms that preclude implementation of its findings until further data are forthcoming.2 Recommendations from poison information centres, as described in our article, have not been changed and still provide useful guidance on selecting patients for hyperbaric oxygen.
We believe that careful neurological examination, including specific testing of cognitive function, is vital in the management of patients. Physicians should use tests with which they are familiar and apply them serially to the same patient. Standardisation of formal cognitive testing for trials was beyond the scope of our clinically orientated article.