Usefulness of Ultrasound View of Larynx in Pre-Anesthetic Airway Assessment: A Comparison With Cormack-Lehane Classification During Direct Laryngoscopy

BACKGROUND: One of the main challenges in anesthesiology is difficult intubation. There are many anatomical parameters for evaluating the feasibility of tracheal intubation; one that can reliably predict a difficult intubation is the Cormack-Lehane classification obtained during direct laryngoscopy. This is an invasive procedure that cannot be performed in an awake patient or for pre-anesthetic airway assessments in patients with no prior history of tracheal intubation. Recently, ultrasound has been successfully used for several airway-related applications. OBJECTIVES: The aim of this study was to compare and correlate the ultrasound view of the larynx with the Mallampati classification before anesthesia and the Cormack-Lehane classification during direct laryngoscopy under general anesthesia. METHODS: This cross-sectional descriptive-analytic study included 53 ASA class I - III patients aged 18 - 70 years who were scheduled for tracheal intubation under general anesthesia. Before anesthesia, an oblique transverse ultrasound view of the airway was obtained; in addition, the total time taken to achieve the final plane, the depth of the pre-epiglottic space, and the distance from the epiglottis to the mid-point between the vocal cords were all recorded. The ultrasound measurements were then compared with the Mallampati class on the preoperative evaluation and with the Cormack-Lehane grade during direct laryngoscopy under general anesthesia. RESULTS: It was observed that correlations between the pre-epiglottic space (PE) and Cormack-Lehane grades I, II, and III were weak. Correlations between the distance from the epiglottis to the vocal cords (E-VC) and Cormack-Lehane grades I, II, and III were also weak. The PE/E-VC ratio for correlations between the sonographic view and laryngoscopy had 87.5% sensitivity and 30% specificity. There was no correlation between Mallampati class and the PE/E-VC ratio (P = 0.566). CONCLUSIONS: Our study revealed weak correlation between PE/E-VC and Cormack-Lehane grade, with 87% sensitivity and 30% specificity. Therefore, we concluded that sonographic measurement criteria are not accurate in airway evaluations before anesthesia.