Assessment of the storz video Macintosh laryngoscope for use in difficult airways: A human simulator study

Abstract

Objectives: Video laryngoscopy has been shown to improve glottic exposure when compared to direct laryngoscopy in operating room studies. However, its utility in the hands of emergency physicians (EPs) remains undefined. A simulated difficult airway was used to determine if intubation by EPs using a video Macintosh system resulted in an improved glottic view, was easier, was faster, or was more successful than conventional direct laryngoscopy.

Methods: Emergency medicine (EM) residents and attending physicians at two academic institutions performed endotracheal intubation in one normal and two identical difficult airway scenarios. With the difficult scenarios, the participants used video laryngoscopy during the second case. Intubations were performed on a medium-fidelity human simulator. The difficult scenario was created by limiting cervical spine mobility and inducing trismus. The primary outcome was the proportion of direct versus video intubations with a grade I or II Cormack-Lehane glottic view. Ease of intubation (self-reported via 10-cm visual analog scale [VAS]), time to intubation, and success rate were also recorded. Descriptive statistics as well as medians with interquartile ranges (IQRs) are reported where appropriate. The Wilcoxon matched pairs signed-rank test was used for comparison testing of nonparametric data.

Results: Participants (n = 39) were residents (59%) and faculty. All had human intubation experience; 51% reported more than 100 prior intubations. On difficult laryngoscopy, a Cormack-Lehane grade I or II view was obtained in 20 (51%) direct laryngoscopies versus 38 (97%) of the video-assisted laryngoscopies (p < 0.01). The median VAS score for difficult airways was 50 mm (IQR = 28–73 mm) for direct versus 18 mm (IQR = 9–50 mm) for video (p < 0.01). The median time to intubation in difficult airways was 25 seconds (IQR = 16–44 seconds) for direct versus 20 seconds (IQR = 12–35 seconds) for video laryngoscopy (p < 0.01). All intubations were successful without need for an invasive airway.

Conclusions: In this simulation, video laryngoscopy was associated with improved glottic exposure, was perceived as easier, and was slightly faster than conventional direct laryngoscopy in a simulated difficult airway. Absence of secretions and blood limits the generalizability of our findings; human studies are needed.