Three groups of patients are going to have minor surgery under general anesthesia with inhaled anesthetics and different ventilatory setting (Tidal volume: 8, 10, 12 ml/kg, respiratory rate: 10/min each). Group A (Sevoflurane) will use sevoflurane, group B (Desflurane) will use desflurane, and group C (Isoflurane) will use isoflurane. It will be observed differences among the groups for ventilatory effects on speed of induction.