Ultrasound as a new tool in the assessment of airway difficulties: An observational study.

BACKGROUND: Prediction of difficult mask ventilation (DMV) is as challenging as difficult laryngoscopy. Ultrasound could be a helpful tool in the prediction of these difficulties. OBJECTIVES: The purpose of this study was to evaluate the ability of pre-operative ultrasound assessment of neck anatomy in predicting DMV and difficult laryngoscopy in patients undergoing during elective surgery requiring tracheal intubation. DESIGN: Prospective, single blind, observational study. SETTING: Operating theatre of a teaching hospital in Italy from April 2018 to July 2018. PATIENTS: A total of 194 patients aged more than 18 years, without neck masses, previous thyroid surgery or tracheotomy undergoing general anaesthesia and tracheal intubation for elective ear, nose and throat-surgery were included in the study. OUTCOME MEASURES: Ultrasound distances were recorded with a linear 6 to 13 MHz ultrasound transducer: measurements included the minimum distance from the thyroid isthmus to skin surface, the minimum distance from the hyoid bone to skin surface (DSHB), the minimum distance from skin to anterior commissure of the vocal cords, the minimum distance from skin to trachea at the level of the jugular notch and the distance from skin to epiglottis midway. The degree of DMV and difficult laryngoscopy was quantified. RESULTS: The mean (SD) of DSHB was 0.88 (0.3) cm in the easy mask ventilation group, 1.4 (0.19) cm in DMV group. The mean of DSHB and of the other ultrasound distances increased according to the DMV and difficult laryngoscopy level. The DSHB was correlated with an increase in the risk for DMV (0.61 [IQR 0.5 to 0.69]). DMV groups were associated with a greater ultrasound-measured DSHB. CONCLUSION: The prospective observational study confirms the relationship between ultrasound assessment of the anterior soft tissues of the neck and difficult laryngoscopy and DMV. DSHB and the other distances extend the available evidence, not only for difficult laryngoscopy but also for DMV.