The goal of this clinical trial is to compare the first-attempt success rate in double-lumen tube intubation. The main question it aims to answer:

Is there any difference in the first-attempt success rate of intubation between using flexible bronchoscopy and a video laryngoscope? Researchers will compare the group using a flexible bronchoscope and video laryngoscope with the group using a video laryngoscope only to see if there is a difference in first-attempt success rate.

Participants will be intubated in one of two interventions.

For double-lumen tube insertion, a video laryngoscope can usually be used. However, because the camera is located at the tip, there can be a difference between the line of sight and the actual glottic view, which may make double-lumen tube steering difficult.

Flexible bronchoscopy can guide the double-tube along the natural curvature of the airway with less trauma. In the present research, we hypothesized that the first-pass success rate may differ between a group using video laryngoscopy only and a group using video laryngoscopy and flexible bronchoscopy.

Inclusion Criteria:

1. Scheduled operation
2. Patients required to double lumen tube insertion for thoracic surgery
3. ASA PS 1, 2, 3

Exclusion Criteria:

1. BMI <18.5 or 35.0
2. history of airway surgery
3. suspicious of high aspiration risk
4. Pathology in oropharynx or larynx such as tumor, poly, or inflammation

There can be a national policy for securing individual participant data