A New Formula for Optimal Pediatric Endotracheal Tube Depth by Magnetic Resonance Imaging: Limited Study

ABSTRACT

PURPOSE: The aim of this study is to propose a new, simplified formula using an upper incisor-sternal notch (UI-SN) to predict the airway length of optimal positioning of the endotracheal tube via a midsagittal magnetic resonance imaging (MRI) in pediatric patients. METHODS: Between August 2000 and September 2014, a total of 56 pediatric patients (under 8 years old) who underwent MRI for C-spine or whole spine were included for analysis. Variables, such as curved airway length from upper incisor to carina (UI-C), straight length from upper incisor to sternal notch (UI-SN), and from the clivus to sternal notch (C-SN), were measured. Linear regression was used to analyze the relationship among these variables. RESULTS: The average age was 3.5±2.6, and there were 30 (53.6%) males. The mean airway length for UI-C and UI-SN was 16.0±2.8 and 8.8±2.1 cm, respectively. There was a close linear correlation between UI-C and UI-SN (p<0.001). By linear regression, a formula was obtained as UI-C (cm)=1.26×UI-SN (cm)+5.0 (R²=0.873). CONCLUSION: The airway length from the upper incisor to the carina with the head placed in neutral position can be well predicted by a straight length from the upper incisor to the sternal notch. The proposed simplified formula (UI-C=1.26×UI-SN+5, cm) can provide good guidance in determining the optimal positioning of endotracheal tube in pediatric patients.