Airway ultrasound predicts endotracheal tube size more accurately than Cole’s age-based formula in paediatric patients

Abstract

Background: Age-based formulas (ABFs) are commonly used in paediatric anaesthesia to determine the correct size of an endotracheal tube (ETT). However, these formulas often predict an incorrect size. The aim of this study was to determine if the tracheal internal diameter as determined on axial ultrasound images better predicts paediatric ETT size than Cole’s ABF.

Methods: This study is a prospective observational study that involved 106 paediatric patients aged 1–10 years classified as ASA I and ASA II according to the American Society of Anesthesiologists Classification of Physical Status. These paediatric patients were scheduled for elective surgery and required general anaesthesia. They were randomly allocated to one of two groups by blind balloting. There were 53 participants in each group: the ultrasound-predicted endotracheal tube size (UPE) group and the (agebased) formula-predicted endotracheal tube size (FPE) group. For both groups, the actual ETT size used for intubation was noted and compared to the predicted size.

Results: The two groups (UPE and FPE) were comparable with respect to demographic and clinical variables. Airway ultrasound scans predicted the appropriate ETT size in 52 out of the 53 participants in the UPE group. This is a better prediction than the Cole’s ABF, which accurately predicted appropriate ETT size in 35 out of the 53 participants in the FPE group (p < 0.001).

Conclusion: Data from this study shows that an airway ultrasound scan predicted the ETT size more accurately than Cole’s ABF in paediatric patients.