COMPARISON OF PREOPERATIVE ULTRASOUND-GUIDED AIRWAY ASSESSMENT AND CLINICAL AIRWAY EXAMINATION IN PREDICTING DIFFICULT LARYNGOSCOPY IN ELECTIVE SURGICAL PATIENTS: A PROSPECTIVE OBSERVATIONAL STUDY
Keywords:
Airway ultrasound, Difficult laryngoscopy, Airway assessment, Modified Mallampati grading, Tongue thickness, Skin-to-epiglottis distance, Anterior neck soft tissue, Cormack-Lehane grading, Intubation Difficulty Score, General anaesthesiaAbstract
ackground: The determination of difficult laryngoscopy has often been a tough task for anaesthesia. Despite these situations, standard preoperative airway evaluation is practised. Traditionally performed techniques like the modified Mallampati methods, inter-incisor distance assessment, and assessments of neck mobility have different degrees of reliability which leads to unexpected alterations in the course of anaesthetic management. Airway echography has appeared as a helpful option for the visualization of airway structures. Notably, ultrasound gives more precise measurements of airways. Nevertheless, evidence comparing the parameters obtained by ultrasound to standard clinical evaluation practices is lacking. Objective: This study intends to determine the differential accuracy of ultrasound-guided airway study and traditional clinical airway examination in foretelling difficult intubation in adult patients undergoing planned surgery in general anaesthesia.
Methods: This research was carried out at a teaching tertiary hospital for a period of 12 months. 120 adult patients aged between 18-65 years, belonging to ASA physical status I/II, were enrolled under the study. All of the patients underwent standardized clinical airway evaluation before surgery including Modified Mallampati grading, inter-incisor distance, and neck flexion-extension evaluation of the patients. The patients then underwent ultrasound examination of the airway by high-frequency linear probe to check tongue thickness (TT), skin to epiglottis distance (SED), suprasternal notch anterior neck soft tissue thickness (ANS) and tongue height-to-oral cavity height ratio (TTOHR). The anesthetist doing laryngoscopy remained unaware of the ultrasound result. Modified Cormack-Lehane grading was employed as the gold standard for figuring out challenging laryngoscopy (Grade III/IV) and the Intubation Difficulty Score (IDS) were documented. The diagnostic performance was then evaluated via Receiver Operating Characteristic (ROC) curve analysis, sensitivity, specificity, positive predictive value, negative predictive value, and area under the ROC.
Results: Of the 120 participants, difficult laryngoscopy occurred in 14 (11.7%) patients and difficulty index ≥3 was observed in 16 (13.3%) patients. The airway measurements taken by ultrasound were significantly higher in the patients with difficult laryngoscopy. Mean tongue thickness in patients with difficult airway was 6.02 ± 0.41 cm compared to 5.18 ± 0.29 cm in the patients with easy airway (p <0.001). Skin-to-epiglottis distance and anterior neck soft tissue thickness were also greater in patients with difficult laryngoscopies (p <0.001). The tongue thickness was found to have the best diagnostic ability with an AUROC of 0.91, sensitivity of 85.7%, and specificity of 88.3%, followed by skin-to-epiglottis distance with AUROC of 0.87. The traditional Modified Mallampati grading was less predictive with an AUROC of 0.67/sensitivity of 57.1%. This proves that use of ultrasound is much more reliable in aiding in identification of patients at risk for difficult laryngoscopy.
Conclusion: The use of ultrasound-guided airways before surgery provided a significantly better diagnosis of future difficult intubation than the conventional examination at the bedside. The ultrasound assessments showed high capacity for prediction particularly with regard to tongue fatness and distance between skin and epiglottis, thus making them good assistants in pre-anesthesia examination. Although for large use, the method requires the training of the personnel, possession of the equipment, and elaboration of universal process, it may lead to considerable improvement of the safety of anesthesia and evaluative procedures. Further multiproject investigations involving patients of different types are advisable in order to make the obtained results possible to implement in the assessment system
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