The Measurement of Korean Pediatric Subglottic Transverse Diameter Using Computed Tomography Imaging and Validation of the Formulas for the Appropriate Cuffed Endotracheal Tube

ABSTRACT

PURPOSE: It has been established that the subglottic transverse diameter (SD-T) is the narrowest portion of the pediatric airway. In this study, we aimed to measure SD-T using computed tomography (CT) among Korean pediatrics, and compare and verify the measured SD-T with several formulas for appropriate size of the cuffed endotracheal tube (ETT) in pediatrics. METHODS: This is a retrospective study of 364 children from 0 month to 10 years undergoing facial CT scan. The CT scans were performed in children with spontaneous respiration. We obtained SD-T by these CT scans, and compared them with the Motoyama's formula [internal diameter (ID, mm)=(age/4)+3.5], the formula by Khine et al [ID (mm)= (age/4)+3.0], and the formula by Kim et al [outer diameter (OD, mm)=0.01×age (month)+0.02×height (cm)+3.3]. The obtained ID by these formulas was converted to correspond with OD. RESULTS: SD-T had a strong association with age (Estimate=0.029, R²=0.853, p<0.001), weight (Estimate=0.108, R²=0.698, p<0.001), and height (Estimate=0.048, R²=0.854, p<0.001), according to a linear regression analysis. There was no difference of SD-T between males and females (p=0.636). The intraclass coefficients of OD by the Motoyama's formula and the formula by Khine et al with OD of the cuffed ETT by measured SD-T were high (0.910, p<0.001, 0.897, p<0.001). CONCLUSION: Age based formulas for the appropriate cuffed ETT could be sufficient for emergency endotracheal intubation in Korean pediatrics.