BACKGROUND: In pediatric anesthesia, a method using deliberate endobronchial intubation and auscultation has been used for proper endotracheal tube depth. Tube size, however, may influence on auscultation for air leak between the tube and main bronchus. We attempted to ascertain whether the uncuffed tracheal tube (TT) size affects verifying tube placement by auscultation in children.

METHODS: In 23 children, we measured the distance from the carina to the tip of a tube when the first auscultatory sound could be detected on the left chest and when the breathing sound of both chests equalized during withdrawal from right main bronchus. Then, we compared them with those of either a one-size larger or a one-size smaller tube.

RESULTS: The distance from the carina to the tip at the first sound was significantly longer in the smaller tracheal tube (1.8 cm vs 1.5 cm, P = 0.01). The tube tip at the equalized breath sounds was 0.6 cm below the carina in both tubes.

CONCLUSIONS: These results suggest that detecting endobronchial intubation may be more difficult when using uncuffed tracheal tubes with one-size smaller tube and that auscultation with deliberate bronchial intubation can place the uncuffed TT deeper than an intended depth.