An observational prospective study of performance of acromioaxillosuprasternal notch index in predicting difficult visualisation of the larynx.

Background and Aims: Bedside screening test for predicting difficult intubation is an accepted practice, even though its clinical value remains limited. This study aimed to study the predicting value of acromioaxillosuprasternal notch index (AASI) for difficult visualisation of the larynx (DVL).

Methods: After Hospital Ethical Committee approval, 440 consecutive consenting adult non-obstetric patients were included in this study. AASI, modified Mallampati class (MMT), sternomental distance (SMD), thyromental distance (TMD) and inter incisor distance (IID) were evaluated preoperatively by trained personnel. Visualisation of larynx was graded according to Cormack-Lehane grading, with grade III and IV being considered as DVL. The cut-off values for prediction of DVL were defined a priori . Direct laryngoscopy was carried out by qualified anaesthesiologists blinded to the results of the airway predictors under evaluation. Primary outcome variable was AASI as a predictor of DVL. Comparing DVL with MMT, SMD, TMD and IID were secondary objectives.

Results: DVL was observed in 3.6% [95% confidence interval (1.9-5.4%)] patients. We observed that sensitivity, specificity and Area Under Curve i.e., AUC (95% confidence interval) of ROC of AASI was 81.25 (53.69-95.03), 96.7 (94.39-98.11) and 0.890 (0.777-1.000) respectively. AUC of AASI was found to better than MMT, SMD, TMD and IID.

Conclusion: AASI (≥0.5) is a good predictor of difficult visualisation of the larynx at direct laryngoscopy.