In France, there is actually no recommandation about capnography monitoring in recovery rooms. Nevertheless, some patients are still ventilated in post-anesthesia care units during awakening period. Alveolar hypoventilation could induce moderate hypercapnia, thereby stimulate central ventilatory command. However, this hypoventilation could delay the clearance of anesthetic gases. Capnometry monitoring could influence ventilation applied to these patients. Recovery rooms nurses would perform moderate hyperventilation in response to hign capnometry values. This method could enhance gases elimination, with faster spontaneous breathing recovery and extubation. Length of stay in recovery room could also be shortened. An objective surrogate of ventilation is maximal End Tidal CO2, if there is no alveolo-capillary gradient abnormality (Obesity, Chronic respiratory disease, Cyanogenic heart disease). Thus, this study will compare the percentage of patients who reached a maximum End Tidal CO2 greater than 45mmHg during awakening period in post-anesthesia care unit (PACU) in 2 groups :