High-flow nasal oxygen vs standard care to prevent low oxygen levels during gastroscopy.

High flow humidified nasal oxygen. Oxygen administered via the Optiflow THRIVE device to patient via soft prongs inserted in the nose, at a flow rate of 50-70 L/min as tolerated, humidified using the Fisher and Paykel 850 humidifier, to a humidity of 70% relative humidity. The oxygen concentration delivered from the device will be 100%, but the actual inspired oxygen concentration will vary with the patient's inspiratory flow rate and degree of air entrainment. In the intervention group, patients will be put on a THRIVE device with oxygen delivering at 30 L/min immediately upon entering the room, but before sedation administration. The oxygen delivering rate will be increased to 70 L/min via the THRIVE device immediately after sedation agent is given and will be maintained at 70 L/min during the procedure. The flow rate can be increased up to 100 L/min if necessary by the anaesthetist or decreased to 30L/min if patient is not tolerating the device. Each gastroscopy procedure will be monitored by an observer who will be recording clinical information on a standardised case report form. All departures from protocol will be noted on this form. The gastroscopy procedure will only commence once a clinically appropriate level of sedation is reached, titrated by the anaesthetist. As such, oxygen administration will have occurred for a minimum of 3-5 minutes before the procedure begins. Oxygen delivery will continue until the conclusion of the gastroscopy procedure, and will be removed when the patient is stable for transfer to the recovery room, as judged by the anaesthetist. Typically gastroscopy lasts 5-10 minutes, so in most cases patients will receive the intervention for 8-15 minutes.