For tracheal intubation with a lightwand, adequate bending angle was not exactly investigated. The purpose of the study is compare three bending angles of lightwands for safe and efficient tracheal intubation.

Lightwands are very useful device for difficult airway management due to small moth opening, weak teeth, and cervical spine instability. Experienced clinicians use a lightwand while bending it adequately. However, there has been not previous studies to investigate the adequate angle to bend it.

This randomized controlled trial is to compare three angles (70, 80, and 90 degrees) as bending angle of lightwands for safe and efficient tracheal intubation in cases which require the use of lightwands.

Inclusion Criteria:

• patients who require use of a lightwand for tracheal tubes (i.e. small mouth opening, weak teeth, cervical spine instability)

Exclusion Criteria:

• patients who refuse to participate the study