To investigate the double curve endotracheal tube safely navigate through nasal cavity under guidance of a video-stylet.

we enrolled consecutive patients undergoing oxo-maxillofacial surgery by using video-stylet to establish airway and realize the tube angle changes while advancement, however, patients who did not inform or refuse to enroll into the study still use the video-stylet establish airway. the technique to use videostylet-tube assembly to establish airway is a commonly clinical practice in our hospital.

In general, the endotracheal tube goes through nasal cavity blindly either assist with traditional laryngoscope or video-laryngoscope. Tube advances through selected nasal cavity by using a video-stylet is able to prevent from damages of the abnormal turbinates and tissue mucosa. In addition, we are able to record the stylet angle into nostril, shift axis angle in nasal cavity to prevent orifice and side hole from damaging tissues while tube-stylet assembly advancement, and the angle ranges from initiate intubation to tube advanced into trachea.

the selected nostril is determined by Otolaryngologist who is not aware of the study.

Inclusion Criteria:

• patients undergo regular operation of oro-maxillofacial surgery

Exclusion Criteria:

• easily nasal bleeding, mouth limited (opening mouth < 3cm), hypertension, diabetes, chronic sinusitis with operative history, patients unwilling to be included.

patients undergoing regular oro-maxillofacial surgery are included in the study from a medical university hospital (medical center)