Prediction of Endotracheal Tube Size in Pediatric Population Using Ultrasonographic Subglottic Diameter and Age-Related Formulas: A Comparative Study

BACKGROUND: Choosing the correct Endotracheal tube (ETT) size is important in paediatric patients because an inappropriately large and small sized tube has its own disadvantages and chances of re-intubation with different size tube is high. The currently available modalities do not reflect the actual tracheal diameter for selection of endotracheal tube. Ultrasonography (USG) guided evaluation of transverse diameter at subglottic region may be helpful to estimate the proper size of ETT. We tested the hypothesis that Ultrasound guided subglottic diameter better predicts optimal ETT size than existing methods. AIMS: To predict the appropriate size of ETT in pediatric patients to avoid multiple attempts of intubation and airway edema using simple noninvasive USG-guided methods. SETTINGS AND DESIGN: Design: Prospective study SETTINGS: Tertiary care hospital. MATERIALS AND METHODS: Institutional ethical committee clearance no. BMCRI/PS/138/2020-21 was taken. Laryngoscopy and endotracheal intubation were done in 27 pediatric patients of age 2-15 years using a predetermined-sized ETT, estimated by ultrasonography. ETT size was considered optimal when the cuff leak test was negative. If there was resistance to ETT passage into the trachea, the tube was exchanged with one that was 0.5 mm smaller. If the cuff leak test was positive, then the ETT was exchanged for one with the 0.5-mm larger tube. The comparison was done between the size of ETT calculated by USG-guided subglottic diameter, age, height-related formulas, and clinical methods to look for accuracy of prediction for proper ETT size after cuff leak test. STATISTICAL ANALYSIS: The data collected were entered into Microsoft Excel and analyzed using SPSS version 22. IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp. Appropriate parametric and nonparametric tests were applied wherever necessary. CATEGORICAL DATA: Represented in the form of frequencies and proportions. Continuous data: Represented as mean and standard deviation. Paired sample test: Test to identify the mean difference between two quantitative variables. Kappa statistics: To measure the level of agreement. RESULTS: A total of 27 children of age between 2 and 15 years were selected, out of which 15 were male and 12 were female. The accuracy of predicting appropriate ETT size is greater in ultrasound-guided subglottic diameter when compared to conventional clinical assessment and age- and height-related formula and almost the same accuracy as the clinical method. CONCLUSION: Ultrasound-guided subglottic diameter is an easy, effective, and noninvasive way of predicting accurate ETT size in the pediatric population.