Blood oxygen saturation during anaesthesia with volatile agents vaporized in room air

ANAESTHETISTS have long bees in the habit of administering oxygen-rich gas mixtures. Some administer almost pure oxygen (Johnstone, 1959) and when pulmonary ventilation is allowed to become grossly deficient this is undoubtedly necessary if anoxia is to be avoided. Others take the view that an adequate minute volume should be ensured, and that it is therefore unnecessary to administer more than 20 per cent oxygen (for example, ordinary room air) except in occasional circumstances. In Oxford this latter view is held (Parkhouse and Simpson, 1959) and a clinical trial has been concluded recently, in which 1,250 cases were anaesthetized with volatile agents vaporized in room air. Although this method of anaesthesia is quite satisfactory from the clinical point of view the writers are aware that there is doubt in some anaesthetists ' minds as to whether the patient's colour is always a reliable guide to the adequacy of his arterial oxygen saturation. Accordingly it was decided to make a full investigation of blood oxygen levels during anaesthesia with volatile agents vaporized in room air. PREVIOUS INVESTIGATION