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

Abstract

Objective: We aimed to enhance the prediction of difficult intubation by using ultrasonographic parameters (pre-epiglottic space (Pre-E), distance between epiglottis to middle part of vocal cord (E-VC) and Pre-E/E-VC) adjusting for traditional airway assessments. Material and Methods: This prospective cohort study was conducted at a super-tertiary care hospital in Thailand. Participants aged 18-65 years with ASA classification I-III and who required general anesthesia with endotracheal intubation were included. Preoperative traditional and ultrasonographic airway assessments were performed by two investigators. The outcome was difficult intubations as diagnosed by laryngoscopic view grade 3 or 4. Multivariate logistic regression was used to identify predictors for difficult intubation presented by adjusted odds ratio (OR) and 95% confidence interval (CI). Results: A total of 94 patients were recruited. The incidence of difficult intubation was 15%. The median Pre-E/E-VC ratio among this group was 0.8 compared with 1.0 in the control group (p-value 0.124). The cut-off point of <1.0 of Pre- E/E-VC was not associated with difficult intubation after adjusting for sex and other traditional parameters (p-value 0.11). Predictors of difficult intubation were female sex (OR [95% CI]: 13.8 [2.8, 68.3]), sternomental distance ≤175 mm (OR [95% CI]: 11.6 [1.9, 71.4]) and interincisor gap <4 cm (OR [95% CI]: 19.8 [1.1, 373.8]) with the area under the receiver operating characteristic curve at 0.88 and a specificity of 90.0%. Conclusion: There was no association between the Pre-E/E-VC in predicting difficult intubation in low-risk patients. The ultrasonographic measurements of Pre-E/E-VC were not helpful in predicting difficult intubations in our setting. Trial registration: thaiclinicaltrials.org: TCTR20180115002, Registered 9 January 2018 - Prospectively registered, https:// www.thaiclinicaltrials.org/#