Insertion Depth of Left-sided Double-lumen Tube: a New Predictive Formula

A left-sided double-lumen tube was introduced beyond the vocal cords when the train-of-four stimulation of the ulnar nerve revealed 1 or 2 twitches, the stylet was removed, the double-lumen tube was rotated 90° counterclockwise and then advanced blindly to the predicted depth of insertion.

The optimal position of the double-lumen tube, defined as the inflated endobronchial cuff is placed in the left main bronchus just below the carina without herniation, which was confirmed using a flexible bronchoscope in both supine and lateral decubitus positions.

If the endobronchial cuff was placed too deeply or too proximal, subsequently, the double-lumen tube was withdrawn or advanced, respectively, using the flexible bronchoscope until the optimum position of the double-lumen tube was achieved.