Compare the accuracy of two methods of ultrasound and air leakage test in positioning laryngeal mask. Validate the relationship between ultrasound scores, air leak levels, and bronchoscopic classification in positioning laryngeal mask

Inclusion Criteria:

• patients selected for this study must meet all of the following criterion:

  1. Age is between 17 to 65 years old;
  2. ASA (Amecican Society of Anesthesiology ) scores I-II;
  3. Actual weight is between 30 to 100 kilogram;
  4. Patients undergo selective supine operations under general anesthesia (laryngeal mask);
  5. Patients agree to participate in our study and sign Informed Consent Form

Exclusion Criteria:

• Patients cannot participate in this study if they have any of the following conditions:

  1. Airway stenosis, history of airway masses etc, whicn may cause obstruction to ventilation;
  2. Swelling of the neck caused by huge mass in the neck and history of neck surgery etc, which doesn't contribute to ultrasound observation;
  3. Stomach fullness, intestinal obstruction, gastroesophageal reflux disease etc, which may cause reflux aspiration.