The purpose of this study by automated control of oxygen supply in the immediate postoperative period is to show the possibility of immediate weaning in the postoperative period in case of remifentanil use and complete reversion of curarization.

The main hypothesis of this study is that classical oxygen therapy at 3l/min is futile in the postoperative period of a so-called modern anaesthesia and that a total weaning within one hour after arrival in the ICU is possible whatever the postoperative position of the patient. The aim is therefore to include patients who have to undergo a scheduled surgery under anaesthetic sedation (analgesia with remifentanil) or general anaesthesia (combining remifentanil, propofol rocuronium) for ambulatory surgery. The trial is interventional, randomized, monocentric to demonstrate the absence of interest of prolonged postoperative oxygen therapy under specific intraoperative conditions.

Inclusion Criteria:

• Patients managed by the Anesthesia Department of the Foch Hospital;
• Anesthetic sedation (analgesia with remifentanil) or general anesthesia (combining remifentanil, propofol and possibly rocuronium);
• Men or women over 18 and under 80 years of age;
• To benefit from a surgical intervention scheduled > 48 hours in relation to the procedure;
• Scheduled outpatient surgery;
• Have signed a consent form;
• Be affiliated to a health insurance plan.

Exclusion Criteria:

• Pregnant or nursing patients;
• Oxygen dependent preoperatively or at risk of oxygen dependence postoperatively;
• Lung resection surgery;
• Brain surgery (intracerebral neurosurgery); ENT surgery requiring a half-seated position after the operation;
• Being deprived of liberty or under guardianship.