Background: Little information is available about the accuracy of the teeth mark on the laryngeal tube (LT) as a guide to correct placement in children. The aim of this crossover study was to evaluate three methods for optimal insertion depth of the size (#) 2 tube in children weighing 12-25 kg.
Method: In 24 children, the LT #2 was consecutively inserted by three different methods: (A) until the thick teeth mark on the tube was aligned with the upper incisors, (B) until resistance was felt, and (C) by inserting to a depth, previously measured, of the curved distance between the cricoid cartilage and the upper incisor. In each case, the depth of insertion, the degree of effective ventilation, the presence of leakage, and the fibreoptic view were assessed.
Results: Insertion based on the teeth mark led to a shorter insertion depth and a greater incidence of inadequate ventilation compared with the other two methods. There was no difference in the adequacy of ventilation between methods B and C. The vocal cords were more easily identified with methods B (62.5%) and C (75%) than with method A (12.5%).
Conclusions: Insertion of the LT #2 aligned with the teeth mark can result in a shallow insertion depth and inadequate ventilation. The measured distance from the cricoid cartilage to the upper incisor offers alternative guidance for correct LT insertion.