The initiation of respiration after anaesthesia accompanied by passive pulmonary hyperventilation.

Twelve patients anaesthetized with a mixture of nitrous oxide and oxygen were passively hyperventilated, muscular relaxation being provided by d-tubocurarine. Spontaneous respiration commenced when the patients still had a marked respiratory alkalosis; in three patients active pulmonary hyperventilation occurred in the immediate postanaesthetic period. Five patients with a pre-existing respiratory acidosis also started to breathe with a blood carbon dioxide tension below the pre-operative level. It is concluded that, in conditions in which the respiratory centre is not depressed, stimuli arising in the periphery may initiate respiration despite a low arterial blood carbon dioxide tension. The clinical importance of this is discussed.