Regurgitation of stomach contents, as distinct from vomiting, is the result of a sufficiently high intragastric pressure overcoming the competence of the cardia.In the last fifteen years there have been several studies designed to demonstrate the nature of the cardiac sphincter and to evaluate the pressure required to cause retrograde flow through it13zp 3,4. By contrast, there has been much less consideration given to values for intragastric pressure.Our interest in this matter stemmed from anxiety for the pregnant woman with a breech presentation, already in the lithotomy position, requiring general anaesthesia for delivery of the after-coming head. It seemed that the combination of an intra-abdominal mass together with positioning which would raise the mass higher in the abdominal cavity might be expected to raise intragastric pressure above the non-pregnant value. We have set out to determine the magnitude and significance of the increase. METHODSFour groups of patients have been investigated: 23 men, 36 children, 43 non-pregnant women, all for elective surgery under general anasthesia; and 31 pregnant women, at term, for delivery under general anasthesia. No selection was made with regard to height, weight and age although these were recorded. The children ranged in age from 7 months to 12 years.The patients were pre-medicated with an opiate, where appropriate, and all were given atropine or scopolamine. All adults were pre-oxygenated and anaesthesia induced with a sleep dose of thiopentone which was immediately followed by lOOmg suxamethonium. Without attempting to ventilate the lungs, a cuffed endotracheal tube 249

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