Comparison of the Ratio of the Neck Circumference to the Distance between the Outer Ear Canal and the upper Edge of the Manubrium with Cormack-Lehane Score

Failure to maintain airway after induction of general anesthesia or in patients with multiple trauma who need airway resuscitation or oxygen delivery is one of the most common causes of mortality and disability. Therefore, in this study we aimed to investigate the association between the neck circumference and the distance between the outer ear canal and the upper edge of the manubrium compared to Cormack-Lehane score in patients undergoing laryngoscopy.

In this cross-sectional study, the neck circumferential of patients was determined by the location of the thyroid gland in centimeters and the distance between the outer ear canal and the upper edge of the manubrium was determined and divided by the circumference of the neck to achieve the index. In the next step, using the score of Cormack-Lehane, the grading of larynx was assessed and compared with the index.

18 patients (15.65%) had severe laryngoscopy and 97 (84.35%) had easy laryngoscopy. The area under the receiver operating characteristic (ROC) diagram was between 0.5 and 0.6 which was less than 0.6 and indicated that the studied index was not a suitable criterion for assessment of the difficulty of laryngoscopy and was not different from random selection (P = 0.255).

Taken together, the results of our study showed that the ratio of the peripheral neck circumference to distance between the outer canal and manubrium could not be used as a suitable alternative to the Cormack-Lehane score for prediction of difficult intubation.