Ultrasound of the airway.

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.