Comparative study of preoperative airway assessment by conventional clinical predictors and ultrasound-assisted predictors

Abstract

Aims: The aim of this study is to evaluate the effectiveness of airway sonographic parameters as the predictors of difficult laryngoscopy and to evaluate the validity of combined sonographic and clinical tests. Materials and Methods: This prospective and observational study analyzed a sample of 200 patients who were categorized as having easy (Grades 1 and 2) or difficult (Grades 3 and 4) laryngoscopy based on the laryngoscopic criteria of Cormack-Lahane (CL). Sonographic parameters, including the anterior neck soft-tissue thickness at the level of vocal cord (ANS-VC), ANS tissue thickness at the level of hyoid, and ratio of depth of pre-epiglottic space to distance from epiglottis to midpoint of the distance between vocal cords and clinical parameters, including modified Mallampati class, thyromental distance, and hyomental distance ratio (HMDR), were analyzed. Univariate and multivariate regression analysis was used for the statistical analysis. Results: Twenty patients (10%) were categorized as having difficult laryngoscopy. Statistically significant differences between patients with difficult and easy laryngoscopy were noted for 5 of 6 parameters. The diagnostic validity profiles showed variable sensitivity (26.5%–87.5%) and good specificity (58.9%–94.2%) and negative predictive value (88.8%–97.03%). ANS-VC has the highest sensitivity (87.50%) and area under curve value (0.887), whereas HMDR showed highest specificity (94.2%) and highest accuracy (89.60%) which means it has low false-positive prediction rate. The combination of tests improved the diagnostic validity profile (highest area under the curve, 0.897). Conclusion: Sonographic predictors can help in identifying difficult laryngoscopy. Combined clinical and ultrasonographic parameters showed better validity profiles in comparison to the individual tests.

Prediction of Difficult Laryngoscopy Using Ultrasound: A Systematic Review and Meta-Analysis

“…All but three studies excluded morbidly obese patients (25,8,33). Several studies excluded pregnant patients (7,14,15,23,(34)(35)(36), whereas Xu et al (37) focused exclusively on pregnant patients.…”

“…Patients with known difficult airways or the presence of features likely associated with difficult airways were excluded by most studies (6, 13–25). However, half of the studies did not mention the exclusion of known difficult airway patients (7, 26–39). All but three studies excluded morbidly obese patients (25, 8, 33).…”

“…Ultrasound training and experience were not defined in multiple studies (6, 13, 13, 14, 18, 21, 23–28, 31–33, 35–39). Ultrasound was performed by clinicians with quantifiable experience in three studies (15, 19, 20), and the remaining studies only described the sonographers as having received training or experience (7, 13, 16, 17, 22, 29, 30, 34, 40–42). Two studies performed the ultrasound airway assessment postoperatively (16, 18).…”

Pre-epiglottic Space and Epiglottis to Vocal Cord Ratio in Order to Predict Difficult Intubation in Adults: A Multivariate Analysis

“…In fact, other studies showed a weak association between Pre-E and E-VC ratio and Cormack-Lehane grade. 7,19 Yadav et al 19 reported that anterior neck soft-tissue thickness at the level of the vocal cord had high sensitivity (87.5%) and high area under the curve (0.887) to predict difficult laryngoscopy whereas the pre-E and E-VC ratio had much lower validity profiles. Falcetta et al 16 reported that only the pre-epiglottic area, measured at the thyrohyoid membrane (>5 cm), was the best predictor of a Cormack-Lehane grade of at least 2b on direct laryngoscopy and of difficult intubation but not at the vocal cord level (E-VC).…”

“…This difference might be due to the small number of difficult intubation cases, in which the sample size calculation was only confined to the main exposure (Pre-E and E-VC ratio). Yadav et al 19 found that the combination of traditional clinical and ultrasound parameters can improve the diagnostic validity profile.…”