Is endotracheal tube displacement during head and neck extension due to ascending movement or tracheal lengthening? An observational ultrasonographic study.

Complications of the endotracheal tube (ETT) displacement during head and neck positional changes are related to not only the tip position but also the cuff pressure against the larynx. Here, we evaluated movement of the ETT cuff relative to laryngeal structures as well as tip displacement from the carina.Sixty-two patients scheduled for thyroidectomy were recruited. The distance from the cricoid cartilage to the upper margin of the cuff (CC) and that from the ETT tip to the carina (TC) were measured using ultrasonography and fiberoptic bronchoscopy, respectively, during flexion and extension. The total tracheal length (TTL) was defined as the combination of CC, TC, and the distance from the upper margin of the cuff to the tip.During flexion, the CC and TC were 1.5 ± 0.6 and 2.9 ± 1.0 cm respectively. Seven patients (11.7%) exhibited excessively deep intubation. After adjusting the cuff position under ultrasonography (CC = 0), the tip position was corrected in 96.7%. While the TC increased by 2.1 ± 1.0 cm after the positional change in extension, the CC decreased by 0.6 ± 0.7 cm because the TTL lengthened (1.4 ± 1.1 cm). Four patients (6.7%) exhibited excessive cuff displacement beyond the cricoid cartilage, which could have been corrected under ultrasonography.In conclusion, the ETT cuff displaced toward the larynx in a less degree than the tip did from the carina due to the tracheal lengthening during head and neck extension. Nevertheless, we suggest that ultrasonographic assessment of cuff position may avoid ETT misplacement. Trial registration https://cris.nih.go.kr/ (approval no. KCT0005319); registered on May 14, 2019.