Fiberoptic Evaluation of the LMA(Laryngel Mask Airway) Position During Anesthesia With Spontaneous Respiration or Controlled Ventilation in Children

LMA(Laryngel Mask Airway) is useful for pediatrics surgery, and there are various methods of LMA insertion. When the investigators evaluate the LMA position, the investigators can use fiberoptic bronchoscope (Grade 1 to 4). For pediatric patients, clinical signs(airway pressure\<20cmH2O, expiratory CO2 level)are seen normal but the grade is 3 or 4. And this will bring high risk of aspiration. Recent studies reported the LMA position after general anesthesia induction not after operation. Therefore, the investigators will observe the LMA position three times; after general anesthesia induction, after caudal block, and after operation as well as the difference regarding to spontaneous and controlled ventilation.