Background: Modern, video laryngoscopes provide an easier view of the glottis, possibly facilitating easier intubations. We describe an objective method for evaluating the benefits of video-assisted laryngoscopy, compared with standard techniques using force measurements.
Method: Macintosh and video laryngoscopes (both Karl Storz, Tuttlingen, Germany) were used on the patients until the anesthesiologist was convinced he or she had the best possible view of the glottis. Actual intubation was only performed with the second of the laryngoscopes. Sensors measured the forces directly applied to the patients' maxillary incisors. Additionally, common subjective pre- (e.g., Mallampati) and intraintubation (e.g., Cormack-Lehane [C&L]) metrics of intubation difficulty were evaluated by the anesthesiologists.
Results: All patients (24 female, [50 +/- 16 yr], 20 male [56 +/- 13 yr]) included in the study were successfully intubated with both the classic and video laryngoscopes. The forces recorded for the classic Macintosh blade ranged from 0 to 87.4 N with a median of 15.3 N, whereas the video laryngoscope forces ranged from 0 to 45.2 N, with a median of 2.1 N. The only factor determined to be significantly influential on the associated forces applied to the maxillary incisors was the laryngoscope type (P < 0.01). Video-assisted laryngoscopes reduced the applied forces over standard blades. Mallampati and C&L grade were not predictive of the forces applied.
Conclusions: Video-assisted laryngoscopes seem beneficial when considering forces applied to the maxillary incisors as an objective metric of intubation difficulty. In this study, we could not support that Mallampati and C&L grades predict the forces that are applied to the maxillary incisors.