Radiographic Accuracy and Agreement of the Advanced Paediatric Life Support Age-Based Formula for Endotracheal Tube Insertion Depth in Indian Children Aged 1–12 Years: A Cross-Sectional Analytical Study

Background: Accurate endotracheal tube (ETT) depth is critical in children because short tracheas leave little margin for error. The Advanced Paediatric Life Support (APLS) age-based formula is convenient, but its performance may vary across populations. Objective: To assess the radiographic accuracy and agreement of the APLS age-based formula for predicting ETT insertion depth in children aged 1–12 years. Methods: This six-month cross-sectional analytical study included 74 children aged 1–12 years who required oral endotracheal intubation in the emergency department or paediatric intensive care unit of a tertiary-care hospital. Predicted depth (age in years/2 + 12 cm) was compared with depth measured on post-intubation chest radiographs. Tube position was classified using vertebral landmarks and a safe-distance criterion. Correlation, prediction error and Bland–Altman agreement were assessed. Results: Mean age was 4.83 ± 3.12 years. Mean predicted depth was 14.59 ± 1.75 cm versus a radiographic depth of 13.39 ± 1.99 cm; the mean difference was +1.20 ± 0.76 cm, indicating systematic overestimation. The correlation was strong (r = 0.925, p < 0.001), but the 95% limits of agreement were −0.30 to +2.70 cm. Placement was correct in 28 children (37.8%), too deep in 45 (60.8%) and too shallow in one (1.4%). Mean absolute error was 1.24 cm and root mean square error 1.42 cm. Conclusion: The APLS formula correlated strongly with radiographic depth but showed limited placement accuracy and systematic overestimation. Recommendation: Use the formula only as an initial estimate, and always confirm tube position clinically and radiographically; multicentre studies should evaluate anthropometry-based alternatives.