Anticipation of Difficult Airway by Neck Circumference to Thyromental Distance Ratio

INTRODUCTIONUnanticipated difficult intubation scenario is a major concern for anaesthetists which contributes to perioperative morbidity and mortality. Characteristics of difficult intubation indices like increased neck circumference (NC) and reduced thyromental distance (TM) when combined as a ratio can increase accuracy in predicting difficult intubation. MATERIAL AND METHODSThis prospective, observational study was conducted at Universal College of Medical Sciences Teaching Hospital on 160 patients of ASA class I and II planned for surgery under general anaesthesia with endotracheal intubation. Airway indices measured were modified mallampati classification (MM), thyromental distance, neck circumference, and neck circumference to thyromental distance ratio (NC/TM). RESULTSNC/TM showed the highest sensitivity, specificity, PPV and NPV in the non-obese group (p <0.001) as compared to MM, NC and TM. In the obese group, NC/TM showed the highest sensitivity, PPV and NPV (p <0.001) as compared to NC and TM while the specificity was highest and similar to MM as compared to NC and TM. CONCLUSIONNeck circumference to thyromental distance ratio is a better predictor of anticipating difficult intubation in both obese and non-obese patients compared to modified mallampati classification, thyromental distance and neck circumference.