**4. Role of ultrasonography in the upper airway evaluation**

Point of care ultrasonography (US) has emerged as a novel, simple, portable, noninvasive tool that can be used for airway assessment and management. It plays a pivotal role in the quick assessment of the airway anatomy in emergency areas and the operation room. With the help of US, upper airway imaging can be used for subglottic stenosis detection, prediction of difficult intubation, verification of ETT placement, percutaneous tracheostomy, cricothyroidotomy, post-extubation stridor evaluation, and preoperative determination of pediatric ETT size and double-lumen endobronchial tube (DLT) size [11].

The basic principle behind US image formation by rarefaction needs to be understood clearly for better interpretation of images. Knowledge of US transducer types and its orientation and relevant airway anatomy are important for proper evaluation.
