Predicting uncuffed endotracheal tube size in anesthetized children by ultrasonography: A randomized controlled trial

Abstract

© 2018, Medical Association of Thailand. All rights reserved. Objective: The present study aimed to demonstrate that selecting the endotracheal tube [ETT] size using ultrasound measurement of the subglottic diameter is a more reliable method than an age-based formula. Materials and Methods: Ninety-three patients between 1 and 6 years old undergoing elective surgery under general anesthesia with endotracheal intubation were randomized into 2 groups. In group F (n = 46), a modified Cole formula was used to select the ETT size, while in group US (n = 47), ultrasound measurement ofthe subglottic diameter was used to select the ETT size. The appropriate tube size was clinically determined by leakage at airway pressures of 20 to 25 cmH20. Both groups underwent measurement ofthe transverse subglottic diameter in the supine position during apnea and at inspiratory pressures [IP] of 10 cmH20 and 20 cmH20 before intubation to examine the correlation with the outer diameter ofthe appropriate ETT. Results: The incidence of appropriate ETT size selection in group US was 37 out of 47 (78.7%), which was significantly higher than that in group F (n = 24/46, 52.2%), (p = 0.001). A good correlation was found between the ETT size from ultrasound measurement of the transverse subglottic diameter and the outer diameter of the final proper ETT size, with weighted kappa of 0.59±0.06, 0.75±0.06 and 0.70±0.06 at apnea, 10 cmH20 of IP and 20 cmH20 of IP, respectively. No complications were reported in either group during the study. Conclusion: Ultrasound measurement ofthe subglottic diameter to guide the selection of ETT size yielded the appropriate size more frequently than an age-based formula in anesthetized pediatric patients.