Comparative study on prediction of paediatric endotracheal tube size by ultrasonography and by age based formulas

Abstract

Background: Age-based formulas have been widely used to predict the appropriate size of the endotracheal tube (ETT) for intubation in paediatric age group. These formulas often fail to reliably predict the proper size of ETT. The objective of the study is to determine whether the tracheal internal diameter imaged by ultrasound is a better predictor of ETT size than age based formulas. Methods: The study included a total of 60 patients of ASA 1 and 2 aged between 2 and 15 years of either sex posted for elective surgery under general anaesthesia. After institutional ethical committee approval and written consent from the parents, anaesthesia was induced as per the protocol. The tracheal diameter was measured after induction of anaesthesia, during mask ventilation prior to intubation. A linear high frequency ultrasound probe (GE venue 40) was used to measure the tracheal diameter. The size of ETT was selected according to the measured tracheal diameter. The leak test and adequate oxygenation/ventilation were the objective tests used to validate the appropriateness of the ETT chosen. The ETT sizes determined by age based formulas and by the use of ultrasound were statistically compared with the appropriate ETT size used clinically for intubation. Results: The estimation of endotracheal tube size with the aid of ultrasound was found to be superior when compared with age based formulas. Ultrasound tube size determination correlated well with clinically used ETT size. Conclusions: Determination of endotracheal tube size by ultrasound is a good predictor of proper sized ETT in paediatric age group when compared with age based formulas.