Obesity prevalence in the population is increasing. Thus a growing number of obese patient need surgical interventions. These patients have a four time higher risk of suffering of serious complication in relation with their airway management compare with non-obese patients. This is explained by an increased incidence of difficulty with the ventilation and intubation of the obese. The time available for the clinician to manage the airway is define by the non hypoxic apnea time. This laps of time is dependent of the oxygen stocks of the patient, which are dependent of the functional residual capacity (FRC) and his oxygen consumption. For a non-obese patient, a normal pre-oxygenation of three minutes at 100% of oxygen allows a non hypoxic apnea time (oxygen saturation > 90%) of 8,9 minutes. However, for the morbidly obese, this time is cut to less than three minutes.