Point-of-care ultrasound in the airway assessment: A correlation of ultrasonography-guided parameters to the Cormack-Lehane Classification

Shelly Rana, Versha Verma, Shyam Bhandari, Shalini Sharma, Vishal Koundal, Sudarshan Kumar Chaudhary, Shelly Rana, Versha Verma, Shyam Bhandari, Shalini Sharma, Vishal Koundal, Sudarshan Kumar Chaudhary

Abstract

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.

Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
Graphical presentation of distribution of patients in easy and difficult laryngoscopy groups. Easy laryngoscopy corresponded to Cormack–Lehane Grade 1, 2; difficult laryngoscopy: Cormack–Lehane Grade 3, 4. The data presented as percentage
Figure 2
Figure 2
Graphical representation of sonographic predicted HMDR, Pre E/E-VC (mean ± SD) to Cormack–Lehane Grading. HMDR: Hyomental distance ratio. Pre E/E-VC: Ratio of depth of preepiglottic space to the distance between epiglottis and midpoint of vocal cord, *P = 0.00; †P > 0.05 (HMDR between Cormack–Lehane 1 and Cormack–Lehane 2)
Figure 3
Figure 3
Correlation of ultrasonography measured hyomental distance ratio to Cormack–Lehane Grades utilizing receiver operating characteristic graphs (P = 0.00)
Figure 4
Figure 4
Graphical presentation depicting correlation of Pre E/E-VC and Cormack–Lehane Grades utilizing receiver operating characteristic graphs (P = 0.00). Pre E/E-VC: Ratio of depth of preepiglottic space to the distance between epiglottis and midpoint of vocal cord

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