[Endotracheal tube selection in children: which is the better predictor for the selection, tracheal internal diameter in X-ray photograph or age-based formula?].

BACKGROUND: Age-based formula has been widely used to predict the appropriate size of the endotracheal tube in children. Tracheal internal diameter in X-ray photograph is reported to show higher correlation with a correct tube than age. In our institution, X-ray photographs were stored as digital images, enabling us to measure tracheal internal diameters more accurately than conventional X-ray films. Therefore, we investigated whether tracheal size in digital X-ray photograph is a better predictor for the tube selection than age. METHODS: We reviewed data from children aged 1 to 8 years for the past 5 years. The data included age, tracheal internal diameter at 6th cervical (C6), 2nd thoracic vertebrae (T2) in X-ray photograph and selected tube size. The tube size was estimated by the age-based formula or on the basis of tracheal size. RESULTS: The endotracheal tube size correlated significantly with the age, and tracheal internal diameter at C6 or T2 in X-ray photograph (correlation coefficients P=0.898, 0.653, and 0.771 respectively; P<0.0001). The tube size predicted by the age allowed appropriate intubation in 62.2%, but that by the tracheal size at C6 and T2 in 42.8% and 43.7% respectively. CONCLUSIONS: The age-based formula is more reliable and appropriate to decide the size of endotracheal tube for children than the tracheal size.