Point‐of‐care ultrasound of the upper airway in difficult airway management: a systematic review and meta‐analysis*

Summary Introduction The utility of bedside screening tests for the prediction of difficult airways is limited. There is growing interest in the role of point‐of‐care‐ultrasound in airway assessment and management. This systematic review and meta‐analysis aimed to determine the diagnostic utility and clinical application of various upper airway point‐of‐care‐ultrasound parameters in the prediction of difficult airways. Methods We searched databases for randomised controlled trials, observational studies and case series with more than five cases. Results In total, 60 studies involving 10,580 patients, evaluating 58 parameters were included. For difficult facemask ventilation, a narrative synthesis showed that increased tongue thickness was associated with an increased incidence of a difficult airway. For prediction of difficult laryngoscopy, the sensitivity, specificity and area under the receiver operator characteristic curve (AUROC) for distance from‐skin‐to‐vocal‐cords were 0.84 (95%CI 0.74–0.91), 0.81 (95%CI 0.61–0.92) and 0.87 (95%CI 0.78–0.89), respectively (high certainty of evidence). For prediction of difficult tracheal intubation, distance from skin‐to‐epiglottis had the highest sensitivity (0.80 (95%CI 0.74–0.85)) and specificity (0.86 (95%CI 0.74–0.91)) (high certainty of evidence), while distance from skin‐to‐hyoid had the highest AUROC of 0.86 (95% CI 0.73–0.92), with a sensitivity and specificity of 0.78 (95%CI 0.60–0.89) and 0.81 (95%CI 0.63–0.91), respectively (moderate certainty of evidence). Ultrasound use was associated with higher first pass success in percutaneous tracheostomy (odds ratio (95%CI) 3.9 (2.1–71), (low‐moderate certainty of evidence)) and improved cricothyroid membrane identification compared with palpation (odds ratio (95%CI) 3.61 (2.20–5.92) (moderate‐high certainty of evidence)). Discussion Upper airway point‐of‐care ultrasound may improve prediction of difficult airways; its use is associated with improved first pass success in percutaneous tracheostomy. Future research should focus on evaluating its use in combination with a focused history and standard bedside examination tests, and in at‐risk patient populations.