Ultrasound of the airway

Abstract

Currently, the role of ultrasound (US) in anaesthesia-related airway assessment and procedural interventions is encouraging, though it is still ill defined. US can visualise anatomical structures in the supraglottic, glottic and subglottic regions. The floor of the mouth can be visualised by both transcutaneous view of the neck and also by transoral or sublinguial views. However, imaging the epiglottis can be challenging as it is suspended in air. US may detect signs suggestive of difficult intubation, but the data are limited. Other possible applications in airway management include confirmation of correct endotracheal tube placement, prediction of post-extubation stridor, evaluation of soft tissue masses in the neck prior to intubation, assessment of subglottic diameter for determination of paediatric endotracheal tube size and percutaneous dilatational tracheostomy. With development of better probes, high-resolution imaging, real-time picture and clinical experience, US has become the potential first-line noninvasive airway assessment tool in anaesthesia and intensive care practice.

Use of ultrasound to assess superior and recurrent laryngeal nerve function immediately after thyroid surgery

“…The arytenoid cartilages appear as hyperechoic shadows below the vocal ligaments. During phonation, the true cords oscillate and move towards the midline unlike the false cords, which remain relatively immobile [4]. In patients without nerve palsy, bilaterally symmetrical movements of the vocal ligaments can be seen on the transverse view and the arytenoids will appear at the same height.…”

Accuracy of identifying the cricothyroid membrane by anesthesia trainees and staff in a Canadian institution

“…Ultrasonography also cannot be used in scenarios where there is subcutaneous air, as anatomical structures distal to the air are not visualized easily using ultrasonography. [13][14][15][16] Additionally, an ultrasonography machine is not always immediately available in an emergency scenario, and the ''boot-up'' time may be unacceptably slow. Other steps required for the use of ultrasonography (e.g., gel application, probe selection, image configuration) further delay the cricothyrotomy.…”

A proposed novel ultrasound-guided percutaneous dilatational tracheostomy technique - the in-plane wire-in-needle approach: study design and rationale for multicenteric randomized controlled clinical trial

“…10 However, intraluminal air prevents the visualisation of structures such as the posterior pharynx and the posterior wall of the trachea with US; therefore, injury to the posterior wall of the trachea cannot be completely avoided. 11 Knowledge and correct placement of the needle is important for safe practice and is paramount to success of US-PDT. Precise needle manipulation is also mandatory.…”