Validation of Ultrasonography derived formula to predict endotracheal tube size in pediatric patients

Determination of appropriate sized endotracheal tube isessential in children.Intubationof pediatric patients with an endotracheal tube (ETT) that is too small mayresult in insufficient ventilation, poor reliability of end-tidal gasmonitoring, leakage of anesthetic gases into the operating room environment,and an enhanced risk of aspiration. In contrast, an ETT that istoo large can cause upper airway damage (e.g., local ischemia, ulceration,scar formation) and the potential for subsequent subglottic stenosis. Age-based formulas are commonly  used toestimate optimal ETT size.  Predictive formulas for appropriate ETTsize have also been based on patient weight and height. However, none of theseformulas are able to determine the appropriate size of the endotracheal tubewith great accuracy. Studieshave shown that agreement rate of these formulas for determining theappropriate endotracheal tube size in paediatric patients is as low as 47-77%.  The result is that repeated laryngoscopiesare often necessary to identify the appropriate tube for individual patients.Recent reports suggest that the diameter of the subglottic upper airway can bedetermined by ultrasonography in young adults and pediatric patients. A new regression formula based on measurement of subglottic diameter byultrasonography has been formulated by Shibasaki et al. Unlike theage based formulas , not many studies have been done to evaluate the  agreement rate of the endotracheal tube sizedetermined clinically  and that determinedby  formula based on ultrasonography.

Inour study we aim to determine the rate of agreement between the clinically optimaland the predicted endotracheal tube size as determined by the regression formula based on ultrasonography of thepaediatric airway