ACROMIO-AXILLO-SUPRASTERNAL NOTCH INDEX [AASI] : A SCREENING METHOD TO PREDICT DIFFICULT LARYNGOSCOPY IN PATIENT UNDERGOING GENERAL ANAESTHESIA AND REQUIRING ENDOTRACHEAL INTUBATION

Abstract

Introduction and Aims: Difficult laryngoscopy [poor visualisation of larynx] is a surrogate indicator of difficult intubation and inability to manage difficult visualisation of larynx (DVL) can be life threatening. This study is performed to assess the ability of new index –Acromio -Axillo-Suprasternal Notch Index to predict difficult laryngoscopy in patient undergoing general anaesthesia in addition to other common predictors. Material and Methods: 100 patients with ASA class I and II candidate for general anaesthesia with endotracheal intubation were enrolled to this study. The four usual tests Modified MallampatiTest[MMT], Ratio Of Height to Thyromental Distance[RHTMD], Neck Circumference/ Thyromental distance, Sternomental distance difference were assessed before induction of anaesthesia. The new test AASI 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 pectoralismajor 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 anaesthesiologist with more than 5 years of experience & who was unaware of the study, A laryngoscopy was done and based on Cormack-Lehane classification, grading of laryngoscopy was recorded. Sensitivity, specificity, positive predictive value and negative predictive value with 95% Confidence Interval for each airway predictor in isolation was studied. Results: DVL observed in 12% patients. We observed that sensitivity,specificity,PPV,NPV,AUC of Roc[95% confidence interval] of AASI was 80%[44.4-97.5%], 95.56%[89-98.8%],66.67%[42.22-84.6%],97.7%[92.6-99.33%},0.985[0.898-0.988]respectively & these results are better than other conventional methods of difficult airway predictors. Conclusion: AASI more than or equal to 0.5 is a good predictor of difficult visualisation of larynx (DVL) at direct laryngoscopy.