"Prediction of Optimal Pediatric Endotracheal Tube Size Aged Based Formula Versus Ultrasonography"

"Ultrasonography technique:~The subglottic diameter was estimated with B-mode ultrasonography (Korean, Siemens, Acuson, x300) with a 10-13-MHz linear probe positioned on the midline of the anterior neck (figure1). The evaluation began by identifying the true vocal folds as paired hyperechoic linear structures that moved with respiration and swallowing before patients were paralyzed. The probe was then moved caudally to visualize the cricoid arch which appears as an arched, rounded and hypoechoic structure (figure2). The transverse air-column diameter was measured at the lower edge of the cricoid cartilage after patients were paralyzed (figure3).~The measurements of the subglottic diameter was used to select the outer diameter of endotracheal tube by the equation \[ETT OD=0.55\*(subglottic diameter)+1.16\] (Shibasaki et al., 2010), since the outer diameter of endotracheal tube differs among different manufactures, we used uncuffed Mallinckrodt tracheal tube with a Murphy's eyes."