Design:
This is a prospective, single blinded, observational study. In case of 2 independent variables in the multiple linear regression analysis, the required sample size was calculated as at least 40 in order to determine the large effect width (f2=0.35) at 0.80 power and 0.05 error levels. Since the study will be carried out with 3 different tube diameters, the sample size has been determined as 120 in total (G\*Power software 3.1.9). In the Bland and Altman method, it was stated that when there are at least 100 observations, the 95% confidence level can be determined in the range of ±0.34s (where "s" is the standard deviation of the differences between the two measurements). For this reason, it is seen that the determined sample number of 120 is also sufficient for the Bland\&Altman method. Power analysis was made with G\*Power 3.1.9.7 statistical package program; group=3, n=127 (n1=42, n2=43, n3=42), α=0.05, Effect Size (f)=0.34; power = 93%.
Methods: Pediatric patients younger than 18 yr old who will be operated in our hospital and intubated with cuffed tubes numbered 4.5, 5.0, and 5.5 under general anesthesia will be included in this prospective observational study. After standard monitoring in the supine position, anesthesia will be induced with a mixture of O2 / air (50/50%) and 8% Sevoflurane, and then vascular access will be established. Intravenous (IV) 2-3 mg/kg propofol and 1 μgr/kg fentanyl will be administered to patients with IV access. For muscle relaxation after loss of consciousness, 0.5 mg/kg rocuronium will be given IV. After the patients are paralyzed, a 3 cm roll pad will be placed under their shoulders and airway ultrasonography imaging will be performed with the head slightly extended and in the supine-neutral position. The linear probe will be placed transversely in the anterior neck of the patients and moved in a cefo-caudal direction to view the cricoid cartilage. The cricoid cartilage appears as a hypoechoic round structure with hyperechoic margins. At this level, the transverse diameter of the subglottic air column will be measured in millimeters (mm) on the USG image. The formulas in the literature and the subglottic transverse trachea diameter measured by ultrasound will be used to select the most appropriate endotracheal tube for the pediatric patients. After the appropriate cuffed tube is attached to the patient, the cuff will be inflated with air through a 5 milliliter (ml) injector, and cuff pressure will be measured with a cuff manometer. The optimal cuff volume will be determined by giving or withdrawing the 0.2 ml volume to ensure optimum cuff pressure (20-25 cmH2O) and this value will be recorded. Demographic data of the patients, subglottic transverse airway diameter measured by ultrasonography, endotracheal tube number placed in the patient, given cuff volume, measured cuff pressure value, tube change requirement, peak airway pressure, operation time and postoperative airway complications (sore throat, desaturation, stridor, hoarseness, cough) will be recorded.
