**6.3 Ultrasound-guided prediction of difficult laryngoscopy in the obese patient**

US-guided anterior neck soft tissue thickness measurement predicts difficult laryngoscopy. The measurement is done from skin to the anterior aspect of trachea at three levels: vocal cord, thyroid isthmus, and suprasternal notch. Soft tissue thickness at the vocal cords level is a better predictor of difficult laryngoscopy in obese patients. Soft tissue at each level can be calculated by averaging the soft tissue thickness in millimeters obtained in the central axis of the neck and 15 mm to the left and right pretracheal soft tissue. Patients having neck circumference of 50 cm

#### **Figure 1.**

*(A) Photograph showing probe placement and zone of insonation (area within purple boundary); (B & C) ultrasound image showing mylohyoid (sky blue), mandible (green), hyoid (dark blue), and dorsal surface of tongue (red). (image credits: Author Dr Venkata Ganesh).*

and pretracheal soft tissue thickness of 28 mm at vocal cords level have difficulty while doing laryngoscopy [13].
