Determination of the True Inclination Angle of the Main Bronchi Relative to the Median Sagittal Plane for Placement of a Left-Sided Double-Lumen Tube.

Objectives: This study aimed to determine the true inclination angle of the main bronchi relative to the median sagittal plane, using CT imaging to help increase accuracy of double-lumen tube (DLT) placement.

Design: In this retrospective study, 2 investigators independently measured normal chest CT scans from 50 male and 50 female patients. To determine the true AP axis, a mid-sagittal plane reference line (MSPRL) was drawn, intersecting the midsternum and the vertebral spinous process at the level of mid-carina. Lines were drawn through the center of each main bronchus to determine the inclination angle with regard to the MSPRL.

Setting: Research was conducted at a single institution, the Los Angeles County and University of Southern California Medical Center.

Participants: Normal chest CT images from 50 women and 50 men.

Main Results: The mean true inclination angle between the main bronchi and trachea in the mid-sagittal plane was 108.4° on the left compared with 96.2° on the right (p<0.0001).

Interventions: No specific interventions were done because this was a retrospective study and CT scan analysis.

Conclusion: The data suggested that the trachea does not merely branch in the horizontal plane but branches posteriorly as well, with a true mean anatomic angle between the left main bronchus and trachea of 108.4°. This finding concurred with the authors' suggestion that the DLT be rotated to 110° counterclockwise instead of the routine practice of 90°. The authors suggest clinicians rotate the DLT an additional 20° counterclockwise and direct the top of the DLT to the 11 o'clock position.