The videoscopic view may not be significantly superior to the directly sighted peroral view during Macintosh-style videolaryngoscopy: a randomized equivalence cadaver trial

Abstract

Purpose: Videolaryngoscopy is widely believed to give a superior view to that obtained by direct laryngoscopy. Published literature suggests this benefit extends to both hyper-angulated and Macintosh-style videolaryngoscopes. Notwithstanding, our clinical experience shows that the videoscopic view with a Macintosh-style videolaryngoscope is often no different or only marginally better than the directly sighted peroral view. Methods: A human cadaver equivalence study was performed in which four experienced laryngoscopists obtained pre-assigned laryngeal views by direct sighting using the single-use Macintosh blades of the GlideScope® Spectrum™ (GS) DirectView Macintosh (DVM) and C-MAC®S videolaryngoscopes. Blinded to the laryngoscopist’s view, two independent observers rated the videoscopic view presented on the proximal video monitor at the same time. Directly sighted and videoscopic views obtained by the laryngoscopist and video scorers were recorded on a visual analogue scale (VAS) for each device as the primary outcome measures and compared. Results: On the VAS, the C-MAC®S videoscopic view revealed only approximately 0.9% more (99% confidence interval [CI], -2.5% to 4.3%) of the laryngeal inlet than the directly sighted view. Using GS DVM, the videoscopic view revealed 6.7% (99% CI, 2.3% to 11.0%) more of the laryngeal inlet than the directly sighted view. Although results for the GS DVM achieved statistical significance, neither device gave a clinically significantly improved videoscopic view compared with the directly sighted peroral view. Conclusion: This study failed to corroborate previously published findings of a clinically significantly improved videoscopic view compared with direct peroral sighting using Macintosh-style videolaryngoscopes. Further study of this class of device is warranted in human subjects.