Evaluation of Two Neck Ultrasound Measurements as Predictors of Difficult Laryngoscopy: a Prospective Trial

Unpredictable laryngoscopic difficulty, especially if difficult ventilation occurs, during standard laryngoscopy, remains a dramatic challenge for anaesthesiologists. Accurate airway assessment should always be performed, but the common clinical screening tests have shown low sensitivity and specificity with a limited predictive value. Ultrasound (US) based airway assessment has been recently proposed as a useful, simple, bedside and non-invasive tool in adjunct to clinical methods, but to date few studies are available about the potential role of ultrasound in difficult airway evaluation and these are mostly limited on specific groups of patients.

The aim of this prospective, single blinded, observational study is to determine the correlation between two neck ultrasound measures assessed at the pre-operative visit and Cormack-Lehane grade view at direct laryngoscopy, assessed at the induction of anaesthesia 24 hours later.

METHODS: During the pre-operative visit (24 hours before surgery), clinical screening tests to predict a difficult airway are performed and the anterior cervical soft tissue's thickness is assesses.

The thickness of the anterior cervical soft tissues is measured at two levels, thyro-hyoid membrane (pre-epiglottis space) and vocal cords (laryngeal inlet), using a US probe 10-13-MHz linear transducer placed in the transverse plane with the patient's head in neutral position.

On each level the distance from the skin in the median axis in cm (mDSE = median distance skin to epiglottis; mVC = median distance skin to vocal cords) and the surrounding Area in cm2 (PEA = pre-epiglottis area; AVC = Area pre vocal cords) are measured.