Comparison of endotracheal tube selection using age-based formulas across body-mass index groups in pediatric patients undergoing nasal intubation for dental treatment under general anesthesia

Aims: Accurate endotracheal tube (ETT) selection is essential for pediatric nasal intubation, especially when using age-based predictive formulas. The modified Motoyama formula, which adjusts for nasal intubation by selecting a slightly smaller internal diameter and adding length to depth, is commonly used. However, its accuracy across different body-mass index (BMI) groups remains uncertain. Methods: This retrospective study included 677 pediatric patients aged 2–10 years who underwent nasal intubation for dental procedures under general anesthesia. Actual ETT internal diameters and insertion depths were compared with values predicted by the modified Motoyama formula. Patients were stratified by BMI percentile into four groups. Statistical comparisons and Bland–Altman analyses were performed to evaluate prediction accuracy and agreement. Results: The median ETT diameter (4.5 mm) closely matched the modified Motoyama estimate (4.25 mm; p=0.054), while the modified Motoyama formula significantly overestimated ETT insertion depth (actual: 15.5 cm vs. predicted: 16.5 cm), with a median difference of –1.5 cm (IQR: –3.0 to 0.0; p