Does the presence of a tracheal bronchus affect the margin of safety of double-lumen tube placement?

During double-lumen tube (DLT) placement, the anesthesiologist must be mindful of the margin of safety. We determined how this margin is affected by the presence of a tracheal bronchus by elucidating the mathematical relationship between some relevant physical dimensions of the trachea, bronchi, and DLT. Our results suggest that a tracheal bronchus only rarely affects the intrinsic margin of safety of DLT placement. When the tracheal bronchus is located much higher than its most frequently seen location (within 2 cm from the carina), however, there is increased risk that it could be blocked by the tracheal cuff of a left-sided DLT.