The Comparison of Two Different Methods of Partial Inflation of Cuff for Facile Insertion of Laryngeal Mask Airway in Pediatric Patients

• The intra-cuff pressure [ Time Frame: approximately 5 to 10 minutes after insertion of LMA. ] [ Designated as safety issue: No ]
  1) After insertion of LMA, we confirm adequate ventilation. And then we measure intra-cuff pressure using cuff pressure manometer. 2) After confirming adequate ventilation, tidal volumes are measured using spirometer sensor attached anesthesia machine. Five corresponding inspiratory and expiratory tidal volumes are recorded and the difference between these is calculated as the leak volume. The time that measures the intra-cuff pressure and leak volume is approximately 5 to 10 minutes after insertion of LMA.
• The leak volume [ Time Frame: approximately 5 to 10 minutes after insertion of LMA. ] [ Designated as safety issue: No ]
  1) After insertion of LMA, we confirm adequate ventilation. And then we measure intra-cuff pressure using cuff pressure manometer. 2) After confirming adequate ventilation, tidal volumes are measured using spirometer sensor attached anesthesia machine. Five corresponding inspiratory and expiratory tidal volumes are recorded and the difference between these is calculated as the leak volume. The time that measures the intra-cuff pressure and leak volume is approximately 5 to 10 minutes after insertion of LMA.

Partial cuff inflation before insertion is generally used for laryngeal mask airway insertion in children. However, it is not proven how much the cuff should be inflated. The aim of this study is to compare efficacy between the method using the resting volume and the method using half the maximum volume for partial cuff inflation.

• Device: The cuff inflation by the resting volume
  80 patients are randomly allocated into two groups : resting volume group (n=40), half the maximum volume group (n=40). In the resting volume group, the pilot balloon valve is connected to syringe without piston for keeping the valve open to the atmosphere and allowing the pressure within the cuff of LMA to equalize with atmospheric pressure. In the half the maximum volume group, the cuff of LMA is completely emptied and then the cuff is filled with the half the maximum volume.
• Device: The cuff inflation by the maximum volume
  80 patients are randomly allocated into two groups : resting volume group (n=40), half the maximum volume group (n=40). In the resting volume group, the pilot balloon valve is connected to syringe without piston for keeping the valve open to the atmosphere and allowing the pressure within the cuff of LMA to equalize with atmospheric pressure. In the half the maximum volume group, the cuff of LMA is completely emptied and then the cuff is filled with the half the maximum volume.

• Experimental: resting volume group
  Intervention: Device: The cuff inflation by the resting volume
• Active Comparator: maximum volume group
  Intervention: Device: The cuff inflation by the maximum volume

Inclusion Criteria:

• children (0-9 years of age)
• children who is scheduled for elective surgery of short duration (less than 2 hr) undergoing general anesthesia using LMA-classic

Exclusion Criteria:

• patients with an abnormal airway
• patients with reactive airway disease
• patients with gastroesophageal reflux disease
• patients with chronic respiratory disease
• patients who has a history of an upper respiratory tract infection in the preceding 6-week period