Hyperventilation in carbon-monoxide poisoning.

The recent revival of interest in the use of 5% or 7% carbogen in the treatment of carbon-monoxide poisoning has prompted the description of four unusual cases in which gross hyperventilation occurred. The investigation of these cases was not very thorough, but such cases are seen so seldom that it is felt that even this incomplete report may be of value in stimulating further research. Hyperventilation in carbon-monoxide poisoning was noted by Haldane (1895) in experiments performed upon himself, but Drinker (1938) concluded that " increased breathing is not a prominent feature." He felt that those patients in whom it occurred would receive especial benefit from inhalation of carbon-dioxide mixtures because Haggard and Henderson (1921) had demonstrated a falling carbon-dioxide content of arterial blood in dogs poisoned with carbon monoxide. A low blood carbon-dioxide content may, however, be due to either respiratory alkalosis (as suggested by Drinker) or to non-respiratory acidosis, and the latter condition would be less likely to benefit from inhalation of carbon dioxide. The pH of the blood would distinguish between these two conditions, but this does not appear to have been measured either in animals or in man. The object of this paper is to report four cases in which hyperventilation was a striking clinical feature, and was accompanied by non-respiratory acidosis. The demonstration of acidosis in these patients not only throws doubt on the advisability of 5% or 7% carbogen as a routine treatment but also contributes to our understanding of why the patients sometimes remain in coma after treatment has removed all but insignificant traces of carbon monoxide from the blood. Methods.-Four patients showing hyperventilation during carbon-monoxide poisoning were studied. An anaerobic blood sample was taken from a brachial artery