• leak pressure of the laryngeal masks [ Time Frame: directly after insertion of the laryngeal mask ] [ Designated as safety issue: No ]
  

• Insertion time and ease of insertion of the laryngeal mask [ Time Frame: during insertion of the laryngeal mask ] [ Designated as safety issue: Yes ]
  

Device: I-gel laryngeal mask, classic laryngeal mask
intubation with airway device

Inclusion criteria of this randomized cross-over study are: BMI > 25, elective surgery in supine position, age>18 years, ASA I-II; Exclusion criteria are: difficult airway, pregnancy, history of reflux or gastrointestinal disorders, abdominal or thoracic surgery; In this cross-over trial both airway devices are inserted in the same patient, the order of insertion is randomized. Patient receive monitoring with blood pressure, ECG and pulse oxymetry during operation. Anaesthesia is induced intravenously using fentanyl (0.001 mg/kg) and propofol (3-5 mg/kg). The I-gel laryngeal mask is inserted with a gastric tube. The classic laryngeal mask was cuffed after insertion with a cuff pressure of 60 cmH2O. The first device is removed 5 minutes after insertion and replaced by the second device. Ease of insertion is graded as very easy=1, easy=2, difficult=3 and very difficult=4. Leak pressure is measured by two tests: In the first test the spill valve is closed at a fresh gas flow of 6l/min and the minimum airway pressure at which gas leaked around the airway device is recorded by listening for an audible leak. In the second test leakage is measured during pressure controlled ventilation. Therefore we administer a fresh gas flow of 3l/min, FiO2 of 50%, inspiration to expiration ratio of 1:2 and a frequency of breathing of 12. Leakage can be measured by the respirator. We record inspiration pressure, mean pressure, plateau pressure, tidal volume and peep at which the first measurable leakage occurred.

For statistical analysis we will use t-tests with a power of 80% and a p < 0.05.