Diagnostic Accuracy of Ultrasound Measurements of Anterior Neck Soft Tissue in Determining a Difficult Airway

Airway management in the emergency department is challenging because conventional screening tools cannot be applied. Therefore, a rapid noninvasive means of identifying a difficult airway will be advantageous for emergency physicians.

The aim of this study is to examine the association between ultrasound measurements of anterior neck soft tissue and difficult airway as judged by the Cormack Lehane grading.

A prospective study was done for 18 months on patients requiring intubation presenting to the emergency medicine department.

Ultrasound measurements of anterior neck soft tissue were obtained in 60 cases at the levels of thyrohyoid membrane, hyoid bone, and vocal cords. Another examiner who was blinded to the ultrasound measurements performed endotracheal intubation and noted Cormack-Lehane grading.

Descriptive statistics such as mean, standard deviation, frequency, and percentage were used. Inferential statistics such as Student's t-test and receiver operating characteristic (ROC) curve analysis were done using the SPSS software version 22.

The thickness of anterior neck soft tissues at the level of hyoid bone in difficult patients was 0.73 cm (95% confidence interval = 0.65-0.80) compared to easy patients 0.47 cm (95% confidence interval = 0.44-0.51) with a P = 0.001 and at the level of thyrohyoid membrane in difficult patients it was 1.83 cm (95% confidence interval = 1.7-1.89) compared to easy patients 1.46 cm (95% confidence interval = 1.41-1.51) with a P = 0.001. Area under the ROC curve was significant at all the three levels with the highest at the level of thyrohyoid membrane 0.99 and least at the level of vocal cords 0.79, the area under the curve was 0.92 at the level of hyoid bone.

Sonographic measurements of the anterior neck soft tissue can be used as a screening tool by an emergency physician to detect difficult intubation.