 Wake up protocol will be the same for all three arms. Normocapnia will be maintained during recovery by mechanical ventilation till spontaneous breathing is resumed. No decrease in the Minute Ventilation is allowed during recovery. Moment of return of spontaneous breathing will be recorded. Once spontaneous breathing is returned, patients will be asked by their name to open their mouth. A positive response will be recorded and the trachea will be extubated. Thereafter, patients will be transferred to the PACU. The parameters listed in the appropriate section will be evaluated. 