AI Summary & Key Takeaways
AI InsightAlthough higher BMI was associated with greater prediction error, this relationship was weak, suggesting that while age-based formulas remain useful, BMI-related variability should be interpreted cautiously when applying these formulas to improve airway safety and accuracy.
📌 3 Key Takeaways
Abstract
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<0.001). BMI showed a weak but significant correlation with prediction errors for both diameter (r=0.165) and depth (r=0.185). No significant variation was found based on chronic disease status. Conclusion: The modified Motoyama formula accurately predicts ETT diameter but tends to overestimate insertion depth in pediatric nasal intubation. Although higher BMI was associated with greater prediction error, this relationship was weak, suggesting that while age-based formulas remain useful, BMI-related variability should be interpreted cautiously when applying these formulas to improve airway safety and accuracy.