Upper Airway Ultrasound Evaluation

Current guidelines support the use of predictive clinical tests in the evaluation of difficult airway, meaning either difficult bag and mask ventilation, conventional laryngoscopy and/or endotracheal intubation. However, despite the clinical use of these predictive tests, unpredictive difficult laryngoscopy complicates 1.5-13% of cases. Life threatening scenarios may be encountered in patients with difficult or impossible bag and mask ventilation. Anaesthesiologists are familiar with the use of ultrasound, with peripheral nerve blockade and central vascular access representing the most popular applications during the last decades. The ultrasound provides real time and accurate images. According to the current literature, there are only a handful of studies relevant to the application of point of care ultrasound (POCUS), as a new tool in the upper airway evaluation. It is a new field of research with high interest. This is a prospective observational study to investigate if specific ultrasound measurements of the anterior neck can serve as predictors of difficult airway. The ultrasound parameters will be measured preoperatively, during the preanaesthetic evaluation, along with standard clinical prognostic tools, like the mallampati score. The ultrasound parameters to be investigated are: 1. the distance from thyroid isthmus to skin surface, 2. the distance from the hyoid bone to the skin surface, 3. the distance from the anterior commissure of vocal cords to the skin surface, 4. the distance from skin to the trachea at the level of jugular notch, 5. the distance from skin to epiglottis corresponding to half of the distance between thyroid cartilage and hyoid bone, 6. and the angle between glottis and epiglottis. After the induction in anaesthesia, the Cormack Lehane score (grading of the laryngoscopy view) and the Han scale (grading of the degree of difficulty of bag and mask ventilation) will also be recorded. The goal of this study is the investigation of the role of POCUS in the evaluation of difficult bag and mask ventilation and difficult intubation. The primary endpoint is the incidence of difficult bag and mask ventilation and the incidence of difficult laryngoscopy and intubation. Secondary endpoints are the correlations between clinical prognostic tools of difficult airway and the POCUS parameters under investigation.