The effect of halothani-nitrous oxide anaesthesia and spontaneous ventilation on arterial blood oxygenation and physiological deadspace

Arterial blood, inspired and expired gas samples were taken from seven patients anaesthetized with halothane (1-2 per cent) and nitrous oxide in oxygen and who breathed spontaneously. Over a two hour period, the average arterial oxygen tension was 75 mm Hg and carbon dioxide tension 49 mm Hg. No significant deterioration of either blood gas value occurred during the two hours. The dead-space/tidal volume ratio and alveolar-arterial oxygen tension difference did not alter significantly during the period of the study.