Prediction of appropriate formula for nasotracheal tube size in developmental disability children

Objectives: Developmental disability children have differences in growth. Therefore, tube size selection is important for nasotracheal intubation. In our previous study for healthy children undergoing dental surgery, height was the most suitable factor to predict nasotracheal tube size. The aim of this study was to find the most suitable formula for selection of nasotracheal tube size for them, retrospectively. Material and methods: Developmental disability children aged 2 to 10 years were included in this study. They were intubated nasotracheally from April 2012 until May 2017. Their actually intubated tube sizes were checked. The predicted tube sizes were calculated according to the formulas by the backgrounds: the diameter of the trachea at the 6th cervical (C6), 7th cervical (C7), and 2nd thoracic vertebrae (T2) in X-ray. The actually intubated tube sizes were compared with predicted sizes. Data were analyzed using Spearman’s regression analysis. Results: The tube sizes with 5.0, 5.5, and 6.0 mm ID were intubated in 75 patients. The age-based formula was the most suitable; the correlation coefficients (r²) were 0.9027 (vs age), 0.5434 (vs height), 0.3779 (vs weight), 0.0785 (vs C6), 0.2279 (vs C7), and 0.3065 (Th2) (p < 0.01). However, 0.5-mm smaller size tubes were more frequently intubated actually. Their correspondence rate to the predicted size was 48% (5.0 mm), 52% (5.5 mm), and 39% (6.0 mm), respectively. Conclusion: The age-based formula could be the most suitable for predicting nasotracheal tube size in developmental disability children aged 2 to 10 years. One smaller size by the age formula was most suitable at first trial tube. Clinical relevance: The present data indicate that the selection of nasotracheal tube using one smaller size by the age formula (ID = 4 + age [years]/4) might be useful for developmental disability children.