Longitudinal ultrasound scan of the neck as part of a routine scan to identify the cricothyroid membrane with the ”String of pearls”^{1, 2} method. The transducer is in the saggital midline over the caudal part of the trachea. The anterior part of the tracheal rings are seen as ”dark pearls on a white string”.  A large pulsating blood-vessel  is seen superficial to the midline of the caudal part of the trachea, cranially to the jugular notch.  

¹ Kristensen MS. Ultrasonography in the management of the airway. Acta Anaesthesiol Scand 2011; 55: 1155-73

² Kristensen MS, Teoh WH, Rudolph SS. Ultrasonographic identification of the cricothyroid membrane: best evidence, techniques, and clinical impact. Br J Anaesth 2016 117 Suppl 1: i39-i48