Comparison of the Karl Storz Video Laryngoscope with the Macintosh Laryngoscope for Intubating Difficult Airway: A Manikin Study

Objective: To compare the Karl Storz video laryngoscope (KSVL) with the conventional Macintosh laryngoscope in simulated difficult airway scenarios, using a Laerdal resuscitation manikin. Methods: This was a prospective comparative study. The scenarios were normal airway, reduced mouth opening, tongue oedema and cervical spine immobilisation. Thirty-five doctors performed endotracheal intubation with both devices in each of the scenarios. The outcome measures were the successful rate of intubation, time taken for intubation, vocal cord visualisation, and ease of intubation. We also surveyed the doctors' preference for the intubation devices. Results: The use of the KSVL resulted in significantly better laryngoscopic grading than the Macintosh laryngoscope in all four scenarios. The mean time of intubation in the cervical spine immobilisation scenario was significantly shorter with the KSVL than the Macintosh laryngoscope (12.56 sec and 14.00 sec, respectively; P=0.049). The mean time of intubation in the tongue oedema scenario was shorter with the KSVL than the Macintosh laryngoscope (19.37 sec and 22.04 sec, respectively), although this was not statistically significant (P=0.546). There was no difference in the mean time required for intubation in the normal and reduced mouth opening scenarios. There was no significant difference in the success rate in all four scenarios. The ease of intubation score of the KSVL was significantly better than that of the Macintosh laryngoscope in all three difficult airway scenarios Conclusions: Our study showed that the KSVL provided a better glottic view in both normal and difficult airways than the conventional Macintosh laryngoscope. It also showed an advantage over the conventional Macintosh laryngoscope in the time required for intubation in patients under cervical immobilisation.