Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study

Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 312 International Journal of Medical and Pharmaceutical Research Online ISSN-2958-3683 | Print ISSN-2958-3675 Frequency: Bi-Monthly Available online on: https://ijmpr.in/ Original Article Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study Dr Ashley Elizabeth Thomas1, Dr Sonia M Lal2*, Dr Sandhya Sudheer3, Dr Ushadevi RS4 1 Junior resident Department of Anaesthesiology, Sree Gokulam Medical College, and Research Foundation, Trivandrum, Kerala, India 2 Associate Professor, Department of Anaesthesiology, Sree Gokulam Medical College, and Research Foundation, Trivandrum, Kerala, India 3 Specialist Anaesthetist, Department of Anaesthesiology, NMC Specialty Hospital, AlNahda, Dubai, United Arab Emirates 4 Professor and Head of the Department, Department of Anaesthesiology, Sree Gokulam Medical College, and Research Foundation, Trivandrum, Kerala, India A B S T R A C T Corresponding Author: Dr Sonia M Lal Associate Professor, Department of Anaesthesiology, Sree Gokulam Medical College, and Research Foundation, Trivandrum, Kerala, India Received: 14-10-2025 Accepted: 29-10-2025 Available online: 12-11-2025 Background: Unexpected difficulty during intubation can lead to serious complications. The Acromio–Axillary–Suprasternal Notch Index (AASI) has been proposed as a simple bedside test for predicting difficult visualization of the larynx (DVL). This study evaluated the diagnostic accuracy of AASI compared with conventional predictors. Methodology: A prospective observational study was conducted in 131 adult patients (ASA I–II) undergoing elective surgery under general anesthesia. Preoperative AASI was measured in the supine position, and the Cormack–Lehane (CL) grade during direct laryngoscopy was recorded by an anesthesiologist blinded to AASI values. Grades I–IIa were classified as easy visualization (EVL) and grades IIb–IV as DVL. Receiver operating characteristic (ROC) analysis determined the optimal AASI cutoff for predicting DVL. Results: DVL occurred in 33.6% (44/131) of patients. Mean AASI was significantly higher in DVL cases (0.53 ± 0.08) than in EVL cases (0.38 ± 0.07; p < 0.001). ROC analysis yielded an AUC of 0.86. The optimal AASI cutoff value (0.46) predicted DVL with 72.7% sensitivity, 87.4% specificity, a positive predictive value of 74.4%, and a negative predictive value of 86.4%. Conclusion: AASI is a simple, non-invasive, and reliable bedside index for predicting difficult laryngoscopy in supine patients. It can complement conventional assessments such as the Modified Mallampati classification, especially when patient cooperation is limited. Further studies with larger populations are warranted to validate its routine use. Copyright © International Journal of Medical and Pharmaceutical Research Keywords: Acromio–Axillary–Suprasternal Notch Index, Airway Predictors , Difficult Airway, Laryngoscopy, Mallampati Classification INTRODUCTION Unanticipated difficulty during endotracheal intubation remains a major cause of anesthesia-related morbidity and mortality, with complications ranging from hypoxia and arrhythmias to cardiac arrest.[1,2] Accurate preoperative prediction of difficult visualization of the larynx (DVL) is therefore essential for effective airway management and improved patient safety. Several bedside screening tests such as the Modified Mallampati classification (MPC), thyromental distance, and sternomental distance have been traditionally used to predict difficult laryngoscopy. However, these tests often show limited sensitivity and specificity and depend on patient cooperation and proper positioning, which may not always be feasible—particularly in critically ill or supine patients.[3–6] In 2013, Kamranmanesh et al. introduced the Acromio– Axillary–Suprasternal Notch Index (AASI) as a novel, objective, and position-independent predictor of DVL.[7] AASI measures the relative depth of the neck into the thorax and can be assessed easily in the supine position. Early studies reported high diagnostic accuracy for AASI, but evidence remains limited, especially among diverse populations.[8,9,10] The Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 313 present study was designed to evaluate the diagnostic accuracy of AASI in predicting difficult visualization of the larynx in adult patients undergoing elective surgery under general anesthesia. We aimed to determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of AASI and to compare its performance with the Modified Mallampati classification. Methodology Study Design and Setting A prospective observational study was conducted in the Department of Anaesthesiology, in a superspeciality medical college hospital from September 2022 to September 2023, after obtaining Institutional Research committee (IRC No: 378/08/2022) and Ethics Committee approval (IEC No: 47/623/09/2022). Participants Adult patients (18–70 years, ASA physical status I–II) scheduled for elective surgeries under general anesthesia with endotracheal intubation were included by consecutive sampling. Patients with head, neck, or thoracic deformities; cervical spine abnormalities; prior head and neck surgery; history of difficult airway; obesity (BMI > 30 kg/m²); obstetric cases; or inability to open the mouth were excluded. Sample size Consecutive sampling was doneconsecutive cases meeting the eligibility criteria was included in the study. Sample size was calculated using sensitivity and specificity. Highest sample size was found to be 131. Measurement of AASI With the patient in the supine position and arms resting alongside the body, a vertical line (A) was drawn from the acromion process to the upper border of the axilla at the level of the pectoralis major. A perpendicular line (B) was extended from the suprasternal notch to intersect line A. The segment above the intersection was designated as line C. The Acromio– Axillary–Suprasternal Notch Index (AASI) was calculated as C/A. Fig 1: Measurement of AASI Airway Assessment and Laryngoscopy Preoperative airway assessment included the Modified Mallampati classification (MPC). Following induction of general anesthesia with standard agents, laryngoscopy was performed in the sniffing position using a Macintosh blade by an anesthesiologist blinded to the AASI values. The laryngeal view was graded according to the modified Cormack–Lehane (CL) scale. Grades I–IIa were classified as easy visualization of the larynx (EVL) and grades IIb–IV as difficult visualization (DVL). Statistical Analysis Data were analyzed using SPSS version 25. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic accuracy of AASI and identify the optimal cutoff value for predicting DVL. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. A p-value < 0.05 was considered statistically significant. Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 314 Results Age distribution 131 patients were enrolled for this study whose age group ranges from 21(minimum) to 70 (maximum) . Majority were of the age group 41-50 years (28.2%) and least patients from the age group 6170 years (9.9%). We noticed that majority patients had EVL, but in elderly (61-70) and younger (21-30)groups , EVL and DVL both had roughly the same prevalence. Table 1: Age distribution Age in years Frequency Percent 21-30 21 16 31 – 40 27 20.6 41 – 50 37 28.2 51 – 60 33 25.2 61 – 70 13 9.9 Total 131 100 Fig 2: Age distribution Fig 3: Age v/s DVL , EVL Table 2: Age v/s DVL , EVL Age EVL DVL Total χ2 df p N % N % N % 21-30 11 12.6 10 22.7 21 16 31 - 40 21 24.1 6 13.6 27 20.6 41 - 50 26 29.9 11 25 37 28.2 0 5 10 15 20 25 30 21-30 31 - 40 41 - 50 51 - 60 61 - 70 Percentage Age in years Age distribution Age in years 0 5 10 15 20 25 30 35 21-30 31 - 40 41 - 50 51 - 60 61 - 70 Percentage Age in years Age distribution EVL DVL Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 315 51 - 60 21 24.1 12 27.3 33 25.2 61 - 70 8 9.2 5 11.4 13 9.9 3.916 4 0.417 Total 87 100 44 100 131 100 Gender distribution Out of 131 patients in total, 63 (48.1% ) were females and 68 (51.9%) were males. Our study is consistent with other studies which state that the incidence of difficult airway is more in males than in females. In this study incidence of DVL in males was 39% and in females was 26%. Table 3: Gender distribution Gender Frequency Percent Female 63 48.1 Male 68 51.9 Total 131 100 Fig 4: Gender distribution Table 4: Gender v/s EVL, DVL EVL DVL Total χ2 df p Gender N % N % N % Female 46 52.9 17 38.6 63 48.1 Male 41 47.1 27 61.4 68 51.9 2.373 1 0.123 Total 87 100 44 100 131 100 Female 48.1% Male 51.9% GENDER Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 316 Fig 5: Gender v/s EVL, DVL BMI Distribution BMI of the patients ranged from 18 to 29.1. BMI > 30 were not included in the study since obesity in itself is a predictor of difficult airway. None of the patients were underweight ( BMI < 18). 86 patients(65% ) were found to have normal weight. 45 patients (34%) were overweight. We studied BMI in these patients and do not see much increase in DVL with increase in BMI. This is probably because the effects of BMI on DVL is more apparent in the Obese ( BMI >30) Table 5: BMI distribution BMI Frequency Percent Normal 86 65.6 Over weight 45 34.4 Total 131 100 Table 6: BMI v/s DVL. EVL EVL DVL Total χ2 df P BMI N % N % N % Normal 57 65.5 29 65.9 86 65.6 Over weight 30 34.5 15 34.1 45 34.4 .002 1 0.964 Total 87 100 44 100 131 100 Fig 6: BMI distribution 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% EVL DVL Gender Male Female Normal 65.6% Over weight 34.4% BMI Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 317 Fig 7: BMI v/s DVL. EVL ASA status distribution ASA physical status I and II were included in the study. 48 patients were ASA I (36.6%) and 83 patients were ASA II (63.4%). We do not see any evident co-relation between ASA physical status and DVL, 37.5 % of ASA I had DVL while 31.3 % of ASA II patients had DVL. Table 7: ASA distribution ASA Frequency Percent 1 48 36.6 2 83 63.4 Total 131 100 Fig 8: ASA distribution Table 8: ASA v/s DVL, EVL EVL DVL Total χ2 df P ASA N % N % N % 1 30 34.5 18 40.9 48 36.6 2 57 65.5 26 59.1 83 63.4 .520 1 0.471 Total 87 100 44 100 131 100 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% EVL DVL BMI Over weight Normal Grade I 36.6% Grade II 63.4% ASA Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 318 Fig 9 : ASA v/s DVL, EVL Mallampatti class distribution Modified Mallampatti classification revealed classes I,II,III and IV among the patients. 37 patients (28.2%) were class I, 65 (49.6%) were class II, 28 (21.4%) were class III and 1 patient was class IV. As expected MMC class I and II had high fraction of EVL .However only one patient was found to have MMC class IV .However a significant fraction of MMC I and II were found to have DVL Table 9: MMC distribution MMC Frequency Percent 1 37 28.2 2 65 49.6 3 28 21.4 4 1 0.8 Total 131 100 Fig 10: MMC distribution 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% EVL DVL ASA Grade II Grade I 0 10 20 30 40 50 60 Grade I Grade II Grade III Grade IV Percentage MMC Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 319 Table 10: MMC v/s DVL, EVL EVL DVL Total χ2 df p MMC N % N % N % 1 23 26.4 14 31.8 37 28.2 2 46 52.9 19 43.2 65 49.6 3 17 19.5 11 25 28 21.4 1.766 3 0.622 4 1 1.1 0 0 1 0.8 Total 87 100 44 100 131 100 Fig 11: MMC v/s DVL, EVL CL Grade distribution Cormack Lehane grading on direct laryngoscopy was recorded as grade I, IIA,IIB, IIIA,IIIB and IV. 54 patients(41.2%) had grade I, 33 patients (25.2%) had grade II A, 14 patients (10.7%) had grade IIB, 19 patients (14.5 %) had grade IIIA and 6 patients (4.6%) had IIIB and 5 patients (3.8%) had grade IV. We see a steady decline in frequency of patients at higher CL grades. The main focus of this study is to establish the co-relation between Line C/A and CL grading. We calculate the average line C for each grade of CL. We see a clear co relation between CL grade and Line C. We see that the mean of Line C increases with the CL grade, starting with Grade II B, which is the grade where difficult air way starts. The difference between the mean line C of each grade and the previous grade, is significant compared to the standard deviation of the line C values. The AASI value increases steadily with increase in CL grade. Due to the positive correlation between the AASI value and the CL grade, the AASI value can be used to predict difficulty in airway in patients. Patients with AASI greater than 0.469 are classified as difficult airway patients, whereas those with AASI lesser than 0.469 are classified as easy airway patients. This is because an AASI value of 0.469 corresponds to a CL grade of II B, which is the onset of difficulty in airway, as per literature. Table 11: CL grade distribution CL GRADE Frequency Percent Grade I 54 41.2 Grade II A 33 25.2 Grade II B 14 10.7 Grade III A 19 14.5 Grade III B 6 4.6 Grade IV 5 3.8 Total 131 100 0 10 20 30 40 50 60 Grade I Grade II Grade III Grade IV Percentage MMC MMC EVL DVL Dr Ashley Elizabeth Thomas et al. Acromio–Axillary–Suprasternal Notch Index (AASI) as a Predictor of Difficult Visualization of the Larynx: An Observational Study. Int. J Med. Pharm. Res., 6 (6): 312‐324, 2025 320 Fig 12: CL grade distribution Table 12: CL grade v/s DVL, EVL CL Grade N LINE C ANOVA Mean sd F p Grade I 54 3.62 0.91 Grade II A 33 3.61 0.81 Grade II B 14 4.60 1.61 25.54 <0.001 Grade III A 19 6.12 2.04 Grade III B 6 6.92 1.53 Grade IV 5 7.60 1.52 Total 131 4.39 1.74 Fig 13: CL grade v/s DVL, EVL Table 13: CL grade V/S AASI CL Grade N AASI ANOVA Mean sd F p Grade I 54 0.361 0.093 Grade II A 33 0.362 0.088 0 5 10 15 20 25 30 35 40 45 Grade I Grade II A Grade II B Grade III A Grade III B Grade IV Percentage CL GRADE 0 1 2 3 4 5 6 7 8 I II A II B III A III B IV CL Grade LINE C