**5. Patient position for ultrasound airway assessment**

Optimal supine sniffing position is achieved by placing a pillow under the occiput to achieve optimal neck flexion and head extension. The presence of air makes it difficult to visualize deeper structures because of poor medium. Comet tail and reverberation artifacts are produced by intraluminal air [8]. Bone structures such as ramus of mandible, mentum, hyoid bone, and sternum appear as bright hyperechoic linear structures with a hypoechoic acoustic shadow beneath it. Cartilaginous structures such as thyroid and cricoid cartilages appear as homogeneous hypoechoic [10]. Muscle and connective tissues appear as heterogeneous striated and hypoechoic. Fat

and glandular structures appear as homogeneous and mildly to strongly hyperechoic when compared with adjacent soft tissues, depending on the fat content. Air-mucosa (A-M) interface appears as bright hyperechoic linear structure.
