The aim of this research would be to determine the efficacy and effects of preoxygenation when performed by the patient (mask held by the patient).

This is the concept of "self-preoxygenation".

Pre-oxygenation is a fundamental element of the induction sequence in anesthesia, described and recommended since 1955. Numerous studies have examined and compared the various techniques for implementing this procedure in terms of duration, objectives, equipment, patient characteristics and conditions. None of them specifies who should hold the mask when carrying out this recommendation. In everyday practice, patients are often asked to hold the mask themselves. A preliminary survey showed that 86% of patients are offered this option. The professionals questioned cited relational reasons (83%) above all, but also organizational reasons (43%).

Inclusion Criteria:

• Patient undergoing scheduled surgery with general anesthesia
• Patient classified ASA I or II
• Patient understanding and speaking French
• Patient informed of the study and not opposed to it
• Decision to have preoxygenation carried out by the patient.

Exclusion Criteria:

• Patients with grade II or III obesity (BMI>35)
• Patient with at least one respiratory comorbidity
• Smoking patient
• Pregnant patients
• Patient with an allergy to one of the mask's components
• Patient with cognitive impairment or known comprehension difficulties
• Patient under guardianship or curatorship
• Patient not affiliated to health care system

Major patient (adults) undergoing scheduled outpatient surgery requiring general anesthesia.