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

Abstract

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. 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. Research was conducted at a single institution, the Los Angeles County and University of Southern California Medical Center. Normal chest CT images from 50 women and 50 men. 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). No specific interventions were done because this was a retrospective study and CT scan analysis. 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.