Direct laryngoscope is a standard equipment for endotracheal intubation. To identify the differences between Macintosh size 3 and 2 blades, we will analysis the data collected from airway and intubation condition.

Selection the most appropriate size of laryngoscope blade size could not only increased intubation successful rate at the first time but also decrease the incidence of tissue trauma. Laryngoscope blade used in daily practice is usually Macintosh 3. However, compared with Caucasian people, Asian people are smaller and thinner especially in women. This study aims to confirm that the Macintosh 2 blade is not inferior to size 3 blade in laryngeal view and intubation rate.

Female patients without known difficult airway will be enrolled and allocated into Macintosh blade size 2 and size 3 groups. The age, body weight, body height, Mallampati classification, mouth opening, thyromental distance, neck circumference, intubation time, Cormack-Lehane grade, intubation difficulty scale scores and associated teeth or tissue traumas will be recorded.

Inclusion Criteria:

• with American Society of Anesthesiologists (ASA) physical status classification 1, 2, or 3
• undergo elective surgery
• receive endotracheal intubation

Exclusion Criteria:

• with known difficult airway (i.e. pathology of the neck, upper airway or alimentary tracts)
• with risks of pulmonary aspiration (i.e. emergent operation, pregnancy or inadequate nil per os)
• with previous difficult intubation history
• intubation attempts more than three times
• patient refusal