An observational study to evaluate the role of ultrasound in the prediction of difficult laryngoscopy

Abstract

Background: Difficult laryngoscopy (DL) is challenging when difficult ventilation occurs during standard laryngoscopy. For airway assessment, the common clinical airway predictors have low sensitivity (Sn) and specificity (Sp) with a limited predictive value. Ultrasound can be a useful tool for predicting such difficulties. We aimed to evaluate the usefulness of several sonographic airway parameters in predicting DL in adults. Patients and Methods: This prospective observational study included 120 patients who underwent elective surgery requiring general anesthesia with direct laryngoscopy (Macintosh blade) and endotracheal intubation. Ultrasonography (USG) assessment included preepiglottic space (PES), hyomental distance (HMD), distance from skin to the hyoid bone-skin (DSHB), and distance from skin-to-epiglottis midway between the hyoid bone and thyroid cartilage distance from skin to epiglottis midway (DSEM). Demographic variables and Cormack-Lehane (CL) grading for laryngoscopy (CL grade 1, 2-easy; 3, 4-difficult). Receiver operating characteristic (ROC) analysis was done, and area under the curve (AUC) was calculated to determine the best predictor of DL. Results: DL was present in 22.50% of patients. Compared to those with easy laryngoscopy, patients with DL had lesser HMD (4.55 vs. 4.96, P = 0.002), and comparable DSHB, DSEM, and PES. Among the various US parameters for predicting DL, we found the highest Sn of DSHB (74.07%); highest Sp of HMD (86.02%); highest positive predictive value of HMD (50%); and highest negative predictive value of HMD (85.1%). ROC curve analysis showed HMD to be the best predictor for DL with the highest AUC of 0.684. Conclusion: DL is common, present in 22.5% patients. US is a novel modality for predicting the DL, especially HMD, which showed the highest AUC among DSHB, DSEM, and PES.