Thus, it is our intent to evaluate the efficiency of application of an inspiratory assistance pressure of 4cmH2O and PEEP 4cmH2O during a 3 minutes pre-oxygenation trial as to the level of FeO2 attained, the rate of attainment of FeO2 > 90% and the tolerance by the patient of the procedure, when compared with a 3 minute trial of the traditional method.