Patients admit to the operation rooms of First Affiliated Hospital of Nanjing Medical University and requiring endotracheal intubation for general anesthesia will be enrolled in this case controlled study.

Patients 1) aged 18 to 70 years; 2) ASA graded I~II class; 3) general anesthesia should be performed under endotracheal intubation, will be included from this study. Patients 1) with organ transplant operations; 2) with thoracic and cardiac vascular surgery; 3) with severe heart or lung disease; 4) BMI over 35kg/m2, will be excluded from this study.

The primary aim is to compare airway clearance for fibreoptic tracheal intubation in each patient position. Secondary outcomes include times to view the vocal cord and carina, the time for tube advancement through the vocal cords, as well as the total time to achieve tracheal intubation.Two anesthesiologists with 5 years of experience in conventional endotracheal intubation and trained for fibreoptic intubation will perform the maneuvers.

Inclusion Criteria:

• aged 18 to 70 years
• ASA graded I~II class
• scheduled for elective surgery requiring orotracheal intubation

Exclusion Criteria:

• with organ transplant operations
• with thoracic and cardiac vascular surgery
• with severe cadiac or pulmonary disease
• BMI over 35kg/m2