ACROMIO-AXILLO-SUPRASTERNAL NOTCH INDEX: A NEW SCREENING TEST TO PREDICT DIFFICULT LARYNGOSCOPY IN GENERAL POPULATION

Background: Airway management expertness is essential in every medical specialty. Inability to manage Difficult Visualization of Larynx (DVL) can be life threatening. This trail was performed to assess the ability of a new index - Acromio-axillo-suprasternal notch index- to predict difficult laryngoscopy in normal population in comparison with the other common predictors. Materials and Methods: 728 consecutive patients with ASA class I & II candidate for general anesthesia with endotracheal intubation were enrolled to this study. The four usual tests MMT, ULBT, RHTMD, NC/TMD were assessed before induction of anesthesia. The new AASI test is calculated as follow: 1) Using a ruler a line is drawn vertically from the top of the acromion process to the superior border of the axilla at the pectoralis major muscle named as line A. 2) A second line is drawn perpendicular to line A from the suprasternal notch (line B); and 3)That portion of line A that lies above where line B bisects line A is line C. AASI is calculated from the length of line C divided by line A(AASI = C/A). By a skilled anesthesiologist who blinded to the assessment, the laryngoscopy was done and based on Cormack-Lehane classification, garding of laryngoscopy was recorded. Sensitivity, specificity, positive predictive value and AUC or ROC for each airway predictor in isolation and comparison with each other was established. Results: The sensitivity of AASI was 66.67% with AUC = 0.790(P = 0.000). But MMT as an old predictive test with NC/TMD and RHTMD with AUC or ROC curve 0.626, 0.531, 0.537 respectively, are not good predictors in this study (P > 0.05). But ULBT with sensitivity 52.38% can be a good predictor (P = 0.003). There are stepwise increases in the incidence of Cormack-Lehane grade III and IV as AASI was greater than 0.6. Conclusion: We considered the value of preoperative assessment of AASI ? 0.6 to be a good and reliable predictor for difficult visualization of larynx