A comparative study of acromio-axillo-suprasternal notch index with upper lip bite test and modified Mallampati score to predict difficult laryngoscopy

Background: The current bedside predictors of the difficult airway are not perfect. A new test, the acromio-axillo-suprasternal notch index (AASI), has been found to be superior to conventional predictors. In this study, we have compared the accuracy of AASI with upper lip bite test (ULBT) and modified Mallampati (MMP) test to predict difficult laryngoscopy and the time taken to complete each test. Methods: Institutional ethical committee clearance was obtained, and written informed consent was taken from 150 patients posted for elective surgery under general anesthesia with endotracheal intubation. Preoperative airway examination was carried out with AASI, ULBT, and MMP score. AASI >= 0.49, ULBT Class III, and MMP score III/IV were considered as predictive of difficult visualization of larynx (DVL). After the induction of anesthesia, the laryngeal view was recorded according to Cormack-Lehane (CL) grade. Sensitivity, specificity, predictive values, and accuracy were calculated for all the three tests. Results: DVL (CL Grades 3/4) was observed in 18 (12%) patients. AASI was found to have higher specificity (93.2%), positive predictive value (PPV) (55%), and accuracy (89.3%) when compared to MMP and ULBT. MMP was found to have the highest sensitivity (77.8%), and ULBT was found to have least sensitivity (50%). Time taken for AASI was higher (13.01 +/- 1.03 s) when compared to ULBT (7.49 +/- 1.95 s) and MMP (3.97 +/- 0.49 s). Conclusion: We conclude that the MMP is the most sensitive and fastest test to predict DVL when compared to AASI and ULBT. AASI is a better predictor for DVL as it has higher specificity, PPV, accuracy, and odds ratio when compared to standard tests such as MMP and ULBT.