The Importance of Evaluation of Neck Circumference to Thyromental Distance Ratio as a Predictor of Difficult Intubation

Abstract

Background: Pre-operative airway assessment for predicting difficult intubation is of utmost importance for anaesthesiologists to ensure adequate oxygenation and ventilation which is a priority. Aims & Objectives: To evaluate the effectiveness of neck circumference (NC) to thyromental distance (TMD) ratio (NC/TMD) as a predictor of difficult intubation and its correlation with established predictors namely Mallampatti grading (MPC grading), Modified Cormack Lehane’s Score (MCLS grading). Methods: 140 patients of age between 18 to 60 years with ASA I, II were selected. Pre-operative, MPC grading and NC to TMD ratio was measured. Intra-operatively, MCLS grading, time taken for intubation, number of attempts taken for intubation, any additional use of equipment required and grading ease of intubation were noted. Correlation was done between them. Results: Out of 140 patients, NC/TMD ratio of >5 was found in 20 patients in which 19 patients required an adjuvant during intubation. NC/TMD ratio had significantly higher sensitivity (75.20) and specificity (99.02) as compared to sensitivity (56.31) and specificity (92.38) of MPC grading. ROC curve for NC/TMD ratio had higher area under curve (AUC = 0.74) than Mallampatti grading (AUC = 0.66). Conclusion: As compared to MPC grading, NC/TMD has emerged out as a better predictor of difficult intubation.

Keywords

• Difficult Intubation
• Mallampati Grading
• Neck Circumference to Thyromental Distance Ratio