The role of ultrasound in appropriate endotracheal tube size selection in pediatric patients.

Background: The aim of this prospective study was to investigate the success of ultrasound in pediatric patients in determining the appropriate sized cuffed endotracheal tube and to compare the results with conventional height-based (Broselow) tape and age-based formula tube size.

Methods: One hundred and fifty-two children of 1-10 years of age, who received general anesthesia for adenotonsillectomy were enrolled to the study. In all participants, the transverse diameter of the subglottis was measured with ultrasound during apnea. An endotracheal tube was chosen with the outer diameter matched to the measured subglottic airway diameter. An age-based (Motoyama-Khine) and height-based (Broselow) endotracheal tube size was calculated. If there was resistance to passage of the tube into the trachea or an airway pressure >25 cmH 0 was required to detect an audible leak, the endotracheal tube was replaced with internal diameter of 0.5 mm smaller. If there was an audible leak at airway pressure <10 cmH O, or peak pressure >25 cmH 0 or a cuff pressure > 25 cmH O was required to seal, the tube was changed to the 0.5 mm larger internal diameter. Best-fit tube internal diameter was the resultant tube internal diameter that met the previously stated conditions. The need for endotracheal tube replacement and peak airway pressure were recorded.

Results: The internal diameter of ultrasound determined tube was the same as best-fit tube in 88% of children. Endotracheal tube was replaced in 15 patients with a one size larger, and in three patients with one size smaller tube. Using Bland-Altman analysis, a better agreement was observed with ultrasound measurement rather than height-based estimation and age-based formulas.

Conclusion: Our findings show that subglottic diameter measured by ultrasound appears to be a reliable predictor for the assessment of the subglottic diameter of the airway in estimating appropriate size pediatric endotracheal tube.