Changes in nasotracheal tube depth in response to head and neck movement in children

Background: A tracheal tube is often inserted via the nasal cavity for dental surgery. The position of the tube tip is important, given that the head position sometimes changes during surgery. Head movement induces changes in the length of the trachea (t-length) and/or the distance between the nare and the vocal cords (n-v-distance). In this study, we investigated the changes in t-length and n-v-distance in children undergoing nasotracheal intubation. Methods: Eighty patients aged 2-8 year undergoing dental surgery were enrolled. After nasotracheal intubation with an uncuffed nasotracheal tube (4.5-6.0 mm), the tube was fixed at the patient's nares. The distance between the tube tip and the first carina was measured using a fibrescope with the angle between the Frankfort plane and horizontal plane set at 110°. The location of the tube in relation to the vocal cords was then checked. These measurements were repeated at angles of 80° (flexion) and 130° (extension). The t-length and n-v-distance were then calculated using these measurements. Results: On flexion, the t-length shortened significantly from 87.5 ± 10.4 mm to 82.9 ± 10.7 mm (P = 0.017) and the n-v-distance decreased from 128.1 ± 10.7 mm to 125.6 ± 10.4 mm (P = 0.294). On extension, the t-length increased significantly from 87.5 ± 10.4 mm to 92.7 ± 10.1 mm (P = 0.007) and the n-v-distance increased from 128.1 ± 10.7 mm to 129.4 ± 10.7 mm (P = 0.729). The change in t-length was significantly greater than that in the n-v-distance. Conclusion: A change in the position of the tracheal tube tip in the trachea depends mainly on changes in t-length during paediatric dental surgery.