Hyperangulated blades or direct epiglottis lifting to optimize glottis visualization in difficult Macintosh videolaryngoscopy: a non-inferiority analysis of a prospective observational study

Abstract

PurposeIt is unknown if direct epiglottis lifting or conversion to hyperangulated videolaryngoscopes, or even direct epiglottis lifting with hyperangulated videolaryngoscopes, may optimize glottis visualization in situations where Macintosh videolaryngoscopy turns out to be more difficult than expected. This study aims to determine if the percentage of glottic opening (POGO) improvement achieved by direct epiglottis lifting is non-inferior to the one accomplished by a conversion to hyperangulated videolaryngoscopy in these situations.MethodsOne or more optimization techniques were applied in 129 difficult Macintosh videolaryngoscopy cases in this secondary analysis of a prospective observational study. Stored videos were reviewed by at least three independent observers who assessed the POGO and six glottis view grades. A linear mixed regression and a linear regression model were fitted. Estimated marginal means were used to analyze differences between optimization maneuvers.ResultsIn this study, 163 optimization maneuvers (77 direct epiglottis lifting, 57 hyperangulated videolaryngoscopy and 29 direct epiglottis lifting with a hyperangulated videolaryngoscope) were applied exclusively or sequentially. Vocal cords were not visible in 91.5% of the cases with Macintosh videolaryngoscopy, 24.7% with direct epiglottis lifting, 36.8% with hyperangulated videolaryngoscopy and 0% with direct lifting with a hyperangulated videolaryngoscope. Conversion to direct epiglottis lifting improved POGO (mean + 49.7%; 95% confidence interval [CI] 41.4 to 58.0; p < 0.001) and glottis view (mean + 2.2 grades; 95% CI 1.9 to 2.5; p < 0.001). Conversion to hyperangulated videolaryngoscopy improved POGO (mean + 43.7%; 95% CI 34.1 to 53.3; p < 0.001) and glottis view (mean + 1.9 grades; 95% CI 1.6 to 2.2; p < 0.001). The difference in POGO improvement between conversion to direct epiglottis lifting and conversion to hyperangulated videolaryngoscopy is: mean 6.0%; 95% CI −6.5–18.5%; hence non-inferiority was confirmed.ConclusionWhen Macintosh videolaryngoscopy turned out to be difficult, glottis exposure with direct epiglottis lifting was non-inferior to the one gathered by conversion to hyperangulated videolaryngoscopy. A combination of both maneuvers yields the best result.Clinical trial registrationClinicalTrials.gov, NCT03950934.

Hyperangulated vs. Macintosh videolaryngoscopy in adults with anticipated difficult airway management: a randomised controlled trial

“…Our findings show that better glottic view with hyperangulated videolaryngoscopy did translate into reduced tracheal intubation time, with higher success rates when used in patients with predicted difficult airways by experienced anaesthetists. Previous study findings [10], as well as the findings of our subgroup analysis show that the highest improvement in POGO occurred when hyperangulated videolaryngoscopy was used to rescue failed Macintosh videolaryngoscopy.…”

“…Hyperangulated videolaryngoscopes are designed to improve glottic view beyond that achieved by devices with less pronounced angulation and may perform better in situations where the glottic view would be restricted severely with Macintosh videolaryngoscopes [10]. A subgroup analysis of a recent Cochrane review reported that hyperangulated videolaryngoscopes were more likely to reduce the incidence of failed tracheal intubation when used in patients with known or predicted difficult airways [9].…”

“…A recent Cochrane analysis showed that Macintosh and hyperangulated videolaryngoscope blades reduce airway-related adverse events compared with direct laryngoscopy [9]. It was uncertain, however, how the blade shape might impact glottic view, success rate and tracheal intubation time, and which blade geometry might be most favourable for a particular patient, individual user or specific clinical context [8,10]. A recent meta-analysis failed to show significant differences in glottic view and tracheal intubation success rate between Macintosh and hyperangulated videolaryngoscope blades; only the tracheal intubation time was increased with hyperangulated blades (mean difference 3.5 s), but this was not considered to be clinically relevant [8].…”