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Updated: Jun 9, 2026
Ultrasonographic Assessment During Cardiopulmonary Resuscitation
Published on: October 24, 2020
Prediction of pediatric endotracheal tube size by ultrasonography
Masayuki Shibasaki1, Yasufumi Nakajima, Sachiyo Ishii
1Department of Anesthesiology and Intensive Care, Kyoto Prefectural University of Medicine, Kyoto, Japan. mshiba@koto.kpu-m.ac.jp
Insights
Ultrasonography measurement of subglottic diameter accurately predicts endotracheal tube (ETT) size in pediatric patients. This method improves upon traditional age and height-based formulas for selecting the correct ETT size.
Area of Science:
- Pediatric Anesthesiology
- Medical Imaging
- Airway Management
Background:
- Standard age and height formulas often inaccurately predict endotracheal tube (ETT) size in children.
- Accurate ETT sizing is critical for safe pediatric intubation.
Purpose of the Study:
- To evaluate if subglottic diameter, measured by ultrasonography, is a better predictor of optimal ETT size compared to existing methods.
- To develop a regression equation for predicting ETT size based on ultrasonographic measurements.
Main Methods:
- 192 pediatric patients (1 month to 6 years) were divided into development and validation groups.
- Subglottic upper airway diameter was measured using ultrasonography before intubation.
- A regression equation was derived to predict ETT size from subglottic diameter.
Main Results:
- Subglottic upper airway diameter strongly correlated with the clinically determined optimal outer ETT diameter.
- The ultrasonography-based prediction showed high agreement: 98% for cuffed ETTs and 96% for uncuffed ETTs.
Conclusions:
- Ultrasonography measurement of subglottic airway diameter reliably predicts appropriate ETT size in pediatric patients.
- This ultrasonographic method offers superior prediction accuracy for ETT size compared to traditional formulas.
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 age-based 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.
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