**6.1 Ultrasound-guided assessment of the subglottic upper airway diameter and prediction of endotracheal tube size**

US has emerged as a reliable tool for assessing the narrowest diameter of the cricoid lumen (transverse diameter). In third decade of life, calcification of the laryngeal cartilages begins to occur because of age factor which creates an acoustic shadow. This limits the use of US in older patients. US-guided subglottic airway diameter measurement is a better indicator of appropriate size of cuffed and uncuffed ETT in pediatric patients.
