Fig. 4From: Use of ultrasound guidance to improve the safety of percutaneous dilatational tracheostomy: a literature reviewLeft parasagittal view at the trachea. A-M, air-mucosal interface; CC, cricoid cartilage; CTA, comet tail artefact; T1-T3, tracheal cartilage. Reprinted with permission from Wolters Kluwer [42]Back to article page