A comparison of pre-oxygenation with patients in the reclined versus supine position

INTERVENTION: 20 women will be randomised to receive oxygen in the usual way. 20 women will receive oxygen in a slightly reclined position. Monitors will be used to determine which group of patients demonstrates the most oxygen stored in their body. Patients will be connected to a breathing machine via a tube placed in their throat after they are asleep. The study also aims to investigate which position (lying flat or slightly reclined) provides the best view of the patient's throat when placing the tube. CONDITION: Surgery: Cholecystomy ; Surgery ; Cholecystomy PRIMARY OUTCOME: Not provided at time of registration SECONDARY OUTCOME: Not provided at time of registration INCLUSION CRITERIA: 40 female patients undergoing cholecystomy.