‘Supercarbia’ in the Anæsthetized Dog

Abstract

ALMOST a hundred years ago, Bert¹ showed that carbon dioxide inhaled in concentrations of 30–50 per cent could cause respiratory failure in the unanæsthetized dog. In subsequent years many anæsthetists and others have become convinced that retention of carbon dioxide can cause respiratory depression and even apnœa in man, but few have recorded their observations.^2,3 Studies in unanæsthetized man are difficult and dangerous; but it was shown that, in one subject, the inhalation of 30 per cent carbon dioxide caused respiratory arrest, probably as a result of convulsions precipitated by the effects of the hypercapnia.⁴ What evidence there is, all points to the fact that concentrations of carbon dioxide in excess of 50 per cent cannot be inhaled without causing respiratory failure.