A Comparative Study of Predicting Difficult Intubation by Six Indexes of Thyromental Height (TMH), Acromioaxillary-Suprasternal Notch Index (AASI), Modified Mallampati Test (MMT), Upper Lip Biting Test (ULBT), Height to Thyromental Distance Ratio (RHTMD), and Neck Circumference to Thyromental Height Ratio (NC/TMH) in Patients Undergoing General Anesthesia

This study aimed to compare the ability of predicting difficult intubation by six indexes of thyromental height (TMH), acromioaxillary-suprasternal notch index (AASI), modified mallampati test (MMT), upper lip biting test (ULBT), height to thyromental distance ratio (RHTMD), and neck circumference to thyromental height ratio (NC/TMH) in patients undergoing general anesthesia. In this cross-sectional study, 600 patients undergoing surgeries were selected, and difficult laryngoscopy was evaluated using above the six tests. The cut-of-point and diagnostic values were determined in comparison with Cormack-Lehane index. The NC/TMH test had the highest sensitivity (80.6%) and AASI had the highest specificity (94.8%). Moreover, among the six testes, NC/TMH had the highest positive predictive value (PPV), and ULBT had highest negative predictive value (NPV). ULBT had the highest positive likelihood ratio and TMH had the highest negative likelihood ratio. Compared with the other tests, NC/TMH, AASI, and TMH had better diagnostic values for evaluating airway, and can be used to detect difficult laryngoscopy.