Background and aim: The sonographic assessment of airway in the preoperative period has encouraging results in predicting difficult laryngoscopy.
Materials and methods: The prospective, observational study was conducted on 120 patients scheduled for elective surgery requiring general anesthesia and tracheal intubation. The depth of the pre-epiglottic space (Pre-E), the distance from the epiglottis to the midpoint of the distance between the vocal cords (E-VC) was measured sonographically. Similarly, hyomental distance ratio (HMDR) was sonographically measured with head in neutral and extended positions. The primary outcome was the efficacy of Pre E/E-VC, HMDR for predicting difficult laryngoscopy (Cormack-Lehane [CL] Grade 3, 4). The secondary outcome was to correlate these parameters to CL grading.
Results: Difficult intubation was observed in 12.5% of patients. The mean ± standard deviation (SD) of Pre E/E-VC ratio was 1.33±0.335, 1.62±0.264 and 1.87±.243, 2.22±.29 for CL Grade 1, 2, 3, and 4, respectively (P = 0.00). The mean ± SD of HMDR was 1.11±.35, 1.12±.29, and 1.07±.39, 1.04 ± 0.01 for CL Grade 1, 2, 3, and 4, respectively (P = 0.00). Pre E/E-VC ratio of more than 1.77 cm had 82% sensitivity, specificity 80%, whereas HMDR less than1.085 had sensitivity 75% and specificity 85.3%, in predicting difficult laryngoscopy (P = 0.00).
Conclusion: The sonographic measurement of the Pre E/E-VC ratio is a better predictor of CL grading as compared to HMDR. The noninvasive prediction of CL grading can be precisely done by Pre-E/E-VC ratio (range: 0-1.425 corresponds to CL Grade 1; 1.425-1.77 ≈ CL Grade 2; 1.77-1.865 ≈ CL Grade 3, more than 1.865 corresponds to CL Grade 4).
Keywords: Anesthesia general; intubation endotracheal; sonography.