The length of the trachea varies and is relatively short in children, it is therefore difficult to determine the correct depth of tracheal tube placement. In 85 children, the tube was placed using one of the following methods: (i) after deliberate endobronchial intubation, withdrawal to the carina was confirmed by auscultation, and the tube was then withdrawn a further 2 cm (auscultation group); (ii) as above, except that withdrawal to the carina was confirmed by a decrease in peak inspiratory pressure (pressure group); (iii) the tube was placed with a 3.0-cm mark at the vocal cords (mark group). The mean (SD) distance from the tip of the tube to the carina was 1.91 (0.81) cm in the auscultation group, and 1.93 (0.67) cm in the pressure group. These were not significantly different (p > 0.05) from targeted distance of 2 cm. In the mark group, the tube was located 2.30 (0.98) cm above the carina in children younger than 36 months and was further from the carina [6.16 (1.0) cm] in older children. In 20% of patients initially randomly allocated to the mark group, the mark could not be visualised. In conclusion, the methods described above effectively achieve adequate tracheal tube depth in children.

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