Efficiency of two variable performance techniques of oxygen therapy in relieving postoperative hypoxaemia

The efficiency of two patient-dependent, variable performance techniques of oxygen therapy in relieving hypoxaemia after upper abdominal surgery was compared. A high-flow system delivered a humidified mixture of oxygen 2 litre min-1 and air 13 litre min-1 through a cannula inserted into the anterior nares. The low-flow system delivered 2 litre min-1 of dry oxygen into the nasopharynx through a catheter. Thirteen otherwise healthy patients received either high-flow oxygen therapy for 30 min followed by low-flow oxygen therapy for a further 30 min after operation or the same therapy in reverse order. With the patients breathing room air, arterial hypoxaemia could be demonstrated with Pao2 inversely related to age. The increase of Pao2 during either oxygen treatment was significantly greater with the low flow system.