Comparison of Ultrasound Parameters and Clinical Parameters in Airway Assessment for Prediction of Difficult Laryngoscopy and Intubation: An Observational Study.

Abstract

Background and objective The primary responsibility of the anesthesiologist is to provide adequate oxygenation and ventilation to the patient by securing the airway. Prediction of Cormack-Lehane (CL) grading preoperatively helps patients' airway management during anesthesia induction, particularly in difficult intubations. Our study aims to evaluate airway assessment modalities using ultrasound and conventional clinical screening methods for predicting difficult laryngoscopy and intubation. Materials and methods This prospective observational study was conducted on 100 patients aged between 18 and 70 years belonging toASA classes I, II, and IIIscheduled for elective surgery requiring general anesthesia under endotracheal intubation was included in the study. Patients who needed rapid sequence induction and had a history of difficult intubation, obese patients with a body mass index (BMI) of more than 40, patients with notable swelling in the neck region (thyroid), pregnant patients, and patients with maxillofacial anomalies were excluded from the study. Clinical parameters such asbody mass index, neck circumference, modified Mallampatigrading, thyromental distance, and ultrasound parameters such as anterior neck soft tissue thickness at the level of the thyrohyoid membrane (ANS-TM) and anterior neck soft tissue thickness at the level of vocal cord (ANS-VC) were obtained preoperatively. After intubation, the CL grading was noted and categorized into two groups: easy (classes 1 and 2) and difficult (classes 3 and 4). Descriptive statistics included frequency and percentage for categorical variables and mean±standard deviation for continuous variables. The chi-square test was applied to find the relationship between easy and difficult laryngoscopy when compared with the outcome for categorical variables. A P value of less than 0.05 was considered significant throughout the study. The receiver operating characteristics curve (ROC curve) was used to determine the sensitivity and specificity to predict the outcomes. Results Ultrasound-guided measurements of ANS-TM and ANS-VC are independent predictors of difficult laryngoscopy compared with clinical screening tests. Of the two parameters, we found that ANS-TM has a better diagnostic value for predicting a difficult airway with an area under the ROCcurve (AUC) of 91% compared with ANS-VC, which has an AUC of 84%. Of the clinical parameters, the modified Mallampati grading has an AUC of 81%, leading to better diagnostic value in the prediction of a difficult airway. Conclusion Our study demonstrated that ANS-TM and ANS-VC are independent predictors of a difficult airway. ANS-TM has a better correlation with CL grading. Clinical screening tests should be combined with ultrasound measurements to aid in the better prediction of difficult laryngoscopy.