Effects of back-up position on tracheal intubation using a Macintosh-geometry videolaryngoscope in patients with a simulated difficult airway: A prospective randomized crossover study

Abstract Background: Both Macintosh-geometry and hyper-angulated videolaryngoscopes provide a better laryngeal view than conventional direct laryngoscope. However, the Macintosh-geometry videolaryngoscopes may not provide as dramatic an improvement in the laryngeal view as the hyper-angulated videolaryngoscopes because they lack the capacity to view structures around corners, so glottic exposure using the Macintosh-geometry videolaryngoscopes may be incomplete in some difficult airway. Patient positioning has an important effect on laryngeal visualization and successful tracheal intubation. However, the ideal head and neck position for videolaryngoscope has not yet been evaluated. We evaluated the effects of the back-up position on laryngeal visualization and ease of intubation using a Macintosh-geometry videolaryngoscope in patients with a simulated difficult airway.Methods: Sixty-four patients were included in this prospective, crossover, randomized controlled trial. Limited neck movement and mouth opening were simulated using a cervical collar. The laryngeal view was assessed in both neutral and back-up positions, in a randomized order, using a Macintosh-geometry videolaryngoscope, based on the percentage of glottic opening (POGO) score and modified Cormack–Lehane (MCL) grade. When scoring laryngeal visualization, external laryngeal manipulation was not permitted. The trachea was intubated only once (in the second position). The ease of intubation was assessed based on the need for optimization maneuvers, Intubation Difficulty Scale (IDS) scores, and time to intubation.Results: The mean POGO score improved significantly in the back-up position (59.4 ± 23.8%) compared with the neutral position (37.5 ± 24%) (P <0.0001). MCL grade 1 or 2a was achieved in 56 (85.9%) and 28 (43.7%) of patients in the back-up and neutral positions, respectively (P <0.0001). Optimization maneuvers for intubation were required in 7 (21.9%) and 17 (53.1%) patients in the back-up and neutral positions, respectively (P <0.0001). The IDS and time to intubation did not differ significantly between positions. Conclusion: The back-up position significantly improved the laryngeal view during Macintosh-geometry videolaryngoscope-guided intubation. It also improved ease of intubation, reflected in a reduced need for optimization maneuvers.Trial registration: This trial was registered with www.clinicaltrials.gov, NCT04716218, on 20/01/2021.