Individually, these techniques of pre-oxygenation are superior to the combination of supine position and no positive pressure. Indeed, studies demonstrated that the beach chair position (derived from the ramped position) or the positive pressure pre-oxygenation in supine position diminished the time needed to obtain a satisfactory pre-oxygenation (End-expiratory oxygen fraction >0,9) and a longer non hypoxic apnea time. Sill, these strategies have never been combined in the same protocol.