Significance of Ratio of the Neck Circumference and Thyromental Distance as a Predictor of Difficult Intubation in Obese Patients

Objective: To ascertain the diagnostic accuracy of raised neck circumference to thyromental distance ratio (NC/TMD) for difficulty in intubation among patients with obesity keeping grades III and IV of Cormack and Lehane's score as the gold standard. Study Design: Cross-sectional validation study. Place and Duration of Study: Anesthesiology Department, Combined Military Hospital Rawalpindi, from Jul to Dec 2017. Methodology: One hundred and thirty obese patients who had to undergo surgery under general anaesthesia were included in the study. All the patients underwent measurement of neck circumference to thyromental distance ratio, and raised neck circumference to thyromental distance ratio was noted. Difficult intubation was labelled according to the grades III and IV of Cormack and Lehane's score. Results: In this study, 130 cases were included. Fifty-eight patients were males, and 72 were females. Diagnostic accuracy of raised neck circumference to thyromental distance ratio for difficulty in intubation among patients who were obese, was recorded where sensitivity was 83.87%, and specificity was found to be 91.92%, positive predictive value as 76.47%, negative predictive value as 94.79%, the accuracy rate was calculated as 90%. Conclusion: Our study showed that difficulty in intubation is more frequent in patients who are obese and the neck circumference to thyromental distance ratio is a reliable method for foreseeing difficult intubation compared to other established predictors with cut off value of 5.0.