Acromio-Axillo-Suprasternal Notch Index Performance in Predicting Difficult Visualization of the Larynx: An Observational Prospective Study

Bedside screening tests for predicting difficult intubation play a crucial role in clinical practice, although their utility remains limited. This prospective observational study aimed to assess the predictive value of the Acromio-Axillo-Suprasternal Notch Index (AASI) for difficult visualization of the larynx (DVL). Following approval from the Institutional Ethics Sub-Committee (Research Protocol No.: IESC/FP/68/2023), this prospective, observational, single-center study involved a sample size of 100 consecutive adult patients, both male and female, aged 20 to 65 years. The participants were classified as American Society of Anesthesiologists (ASA) grade I or II and were scheduled for elective surgeries necessitating endotracheal intubation. Before the operation, the following factors were assessed: AASI, modified Mallampati test (MMT), sternomental distance (SMD), thyromental distance (TMD), and inter-incisor distance (IID). Larynx visualization was evaluated using the Cormack-Lehane (CL) grading system, where grades III and IV indicate difficult laryngeal visualization. Qualified anesthesiologists performed direct laryngoscopy while remaining unaware of the outcomes of the airway predictors being assessed. The main aim of the investigation was to assess the efficacy of the AASI as a means of predicting DVL. The research study's secondary goals involved evaluating the accuracy of AASI in predicting challenging airways compared to other predictors such as MMT, SMD, TMD, and IID. DVL was observed in 21% of patients, out of which 10 and 11 were males and females, respectively. The sensitivity, specificity, and area under the curve (AUC) of the AASI were observed and reported with a 95% confidence interval (CI), being 98.73% (93.2-99.9%), 71.43% (47.8-88.7%), and 0.851 (0.732-0.970), respectively. AUC analysis revealed that AASI outperformed MMT, SMD, TMD, and IID as a predictor of DVL. AASI (≥0.5) serves as an excellent predictor for DVL during direct laryngoscopy. This finding suggests the clinical utility of AASI in identifying patients who may require special consideration during intubation procedures.