Prediction of Pediatric Endotracheal Tube Size by Ultrasonography

Abstract

Background: Formulas based on age and height often fail to reliably predict the proper endotracheal tube (ETT) size in pediatric patients. We, thus, tested the hypothesis that subglottic diameter, as determined by ultrasonography, better predicts optimal ETT size than existing methods. Methods: A total of 192 patients, aged 1 month to 6 yr, who were scheduled for surgery and undergoing general anesthesia were enrolled and divided into development and validation phases. In the development group, the optimal ETT size was selected according to standard agebased formulas for cuffed and uncuffed tubes. Tubes were replaced as necessary until a good clinical fit was obtained. Via ultrasonography, the subglottic upper airway diameter was determined before tracheal intubation. We constructed a regression equation between the subglottic upper airway diameter and the outer diameter of the ETT finally selected. In the validation group, ETT size was selected after ultrasonography using this regression equation. The primary outcome was the fraction of initial cuffed and uncuffed tube sizes, as selected through the regression formula, that proved clinically optimal. Results: Subglottic upper airway diameter was highly correlated with outer ETT diameter deemed optimal on clinical grounds. The rate of agreement between the predicted ETT size based on ultrasonic measurement and the final ETT size selected clinically was 98% for cuffed ETTs and 96% for uncuffed ETTs. Conclusions:Measuring subglottic airway diameter with ultrasonography facilitates the selection of appropriately sized ETTs in pediatric patients. This selection method better predicted optimal outer ETT diameter than standard age-and height-based formulas.

Comparative study on prediction of paediatric endotracheal tube size by ultrasonography and by age based formulas

“…These formulas which are based on age are often unreliable and may end up in repeated laryngoscopy for selecting the correct sized ETT. 4,5 This…”

“…The more advanced methods such as CT and MRI are expensive and impractical. 3,4 We usually depend on age based formulas for selecting appropriate sized endotracheal tubes. These formulas which are based on age are often unreliable and may end up in repeated laryngoscopy for selecting the correct sized ETT.…”

Ultrasonographic Measurement of Subglottic Diameter for Paediatric Cuffed Endotracheal Tube Size Selection: Feasibility Report

“…Visualisation of the paediatric subglottic airway diameter by ultrasonography (USG) can enable a practitioner to better predict ETT size, preventing unnecessary tube changes and airway trauma. Several studies have investigated ideal cuffed tube size selection in paediatric patients; however, all these studies, including those where ultrasonographic measurements were performed (6)(7)(8)(9), selected the initial ETT size according to age-based formulas. However, other than Bae et al (6), who investigated uncuffed tube size, none of these studies actually involved initial placement of an ETT according to ultrasonographic measurements.…”

Ultrasound Imaging in Airway Management: A Boon?

“…Prediction of diameter of left main stem bronchus (for placement of double lumen tube) was found to be quite reliable [13]. US guided measurements have shown good correlation with advance imaging techniques like CT and MRI [12,13]. US has also been utilized for determination of tracheal width and distance from the skin for prediction of tracheostomy tube size and shape [14].…”

“…Prediction of endotracheal tube size by measuring subglottic diameter is useful application of US particularly in paediatric patients [12]. Prediction of diameter of left main stem bronchus (for placement of double lumen tube) was found to be quite reliable [13].…”