Use of ultrasonography as a noninvasive decisive tool to determine the accurate endotracheal tube size in anesthetized children

Background. It is hard to determine the appropriate size and correct tracheal position of endotracheal tube (ETT) in children. The aim of this study is to determine tracheal diameter in children by using ultrasonography technique as objective tool and compare it with commonly used aged based formulas for the ETT size estimation. Patients and methods. Patients undergoing elective surgery in a tertiary children’s hospital were prospectively enrolled. The subglottic transverse tracheal diameter was determined by ultrasonography. An anesthesiologist who was blind to ultrasonographic examination, determined the tube size and performed intubation by evaluating the space between vocal cords with the help of a direct laryngoscopic view. Ultrasonographically measured tracheal diameter, tube diameters, leak/pressure controls, and results of age-based tube size calculations were recorded. Results.A total of 61 patients, mean age of 12 ± 4.21 (2-17) years and mean weight of 38 ± 22.94 (10-106) kg were enrolled. The diameter of trachea measured by ultsonography was 13.0 (11.4-15.1). Outer diameter (mm) of the ETT determined by anesthesiologist was 8.42 ± 1.43; calculated by Cole formula was 9.0 ± 1,42; calculated by Khine formula was 7.67 ± 1.46; calculated by Motoyama formula was 8.33 ± 1.42. ETT cuff was inflated after ETT placement due to leak in 31 (47.7%) patients. Tube was replaced by a larger tube due to excessive leak in one patient. Poor intraclass correlation was found between ultrasonographically determined tracheal diameter and aged based tube diameter calculations (tracheal diameter vs Cole [0.273], Khine [0.207], and Motoyama [0.230]). Conclusion. Ultrasonographical determination of transverse tracheal diameter is a suitable method for determining the correct endotracheal tube size when compared with the age based formulas.