The role of ultrasonography in determination of the appropriate endotracheal tube size selection in pediatric patients
Altun D., Sivrikoz N., Ali A., Orhan Sungur M., Salviz A.E., Çamcı E.
Istanbul University, Dept of Anaesthesiology & Intensive Care, Istanbul, Turkey
Background and Goal of Study: The aim of this prospective clinical study was to investigate the success of ultrasonography (USG) in pediatric patients in predicting the appropriate sized cuffed ETT and compare the results with aged and weight based formulas.
Materials and methods: Children aged between 0-13 years who received general anesthesia with endotracheal intubation were enrolled in the study.
In all participants, subglottic airway diameter was measured with USG and age (Motoyama-Khine) and weight based (Broselow) ETT size was calculated. For USG method, transvers diameter of subglottic airway was measured at the anterior neck at the caudal of the cricoid cartilage without ventilation. ETT size was chosen according to the measured subglottic airway diameter. If there was resistance to passage of the tube into the trachea, a tube one size smaller was replaced. Airway pressures (P) were recorded and if P was above 25 cmH20, ETT was replaced with one size larger. 
Time for the measurement with USG and the need for ETT replacement were recorded. 
A Bland-Altman assessment was used for assess the similarity of two measurement method.
Results: 120 pediatric patients were included. Demographic data are presented in Table 1. 
Gender (f/m)	55 (45.8 %) / 65 (54.2%)
Age (year)	5.4 ± 2.4
Height (cm)	115.5 ± 14.6
Weight (kg)	20.2 ± 6.1
ASA* (I /II) *ASA: American Society of Anesthesiologists	117 (97.5%) / 3 (2.5 %)
[Demographic characteristics of patients]

USG measured diameter was found to be significantly smaller than the diameter as measured by other methods. According to Bland-Altman analysis, measurement with USG was significantly different from age-based calculation (p< 0.001). Likewise, measurement with USG was also significantly different from weight-based calculation (p< 0.001).
In eights patients, ETT was changed with a one size larger tube and therefore success rate with USG was %93.3. The average peak pressure was 17.7±3.0 cm H20 and measurement duration required for USG was 5.1±0.5 seconds. 
Discussion: In this study, USG measurement guided ETT size selection resulted in smaller diameter tubes when compared to age and weight based calculations. Out of the two formulas, weight based calculation was more closely related with USG measurements. 
Conclusion: Our findings show that USG appears to be a reliable predictor for the assessment of the subglottic diameter of the airway in children to estimate the appropriate size ETT for intubation.

The role of ultrasonography in determination of the appropriate endotracheal tube size selection in paediatric patients