In a randomised controlled trial, comparing C-MAC videolaryngoscope (Karl Storz GmbH & Co. KG, Tuttlingen, Germany) with direct laryngoscopy for rapid sequence intubation in emergency patients, Sulser et al.1 showed that the laryngeal visualisation was improved with the C-MAC videolaryngoscope, but better visualisation did not translate into a higher first-pass success rate. Other than the limitations described in the discussion, we note other issues in this study that need to be clarified and discussed.
First, three highly skilled staff anaesthetists performed all tracheal intubations. However, the authors did not clearly describe whether they received adequate training in the use of C-MAC videolaryngoscope and achieved an appropriate level competence with this video device prior to the study. If this was not so, the relative exposure to videolaryngoscopy was likely significantly less than their prior experience with direct laryngoscopy. This is particularly important because the technique used with the C-MAC videolaryngoscope is somewhat different from direct laryngoscopy. For example, during videolaryngoscopic intubation, a main challenge for the intubator is to become familiar with the view on the monitor, and to coordinate eyes and hands appropriately.2 Furthermore, experience with a standard Macintosh laryngoscope does not equate to competence with a videolaryngoscope.3 For the results of a comparative study to be valid and to avoid bias, intubators must be equally proficient with each experimental device. We are concerned that the different learning curves of the intubators for the two studied devices could have biased the findings of this study.
Second, an intubation attempt was defined as insertion of the laryngoscope through the mouth. An important issue neglected by the authors is the advantage of C-MAC videolaryngoscope combining the benefits of direct and videolaryngoscopy in one device; that is, when one option fails at the first attempt the intubator can immediately switch to the other option to successfully complete the intubation (without a second attempt).4 This unique feature of Macintosh-type videolaryngoscopes is exceptionally important for emergency intubation and is significantly different from the angulated and channelled videolaryngoscopes, which can provide only one option. Thus, the definition of a laryngoscopy attempt as used in this study is suitable for a direct laryngoscope or angulated or channelled videolaryngoscopes, but not for a Macintosh-type videolaryngoscope.
Third, it remained unclear whether a stylet was always used for the first intubation attempt. The use of a stylet is very valuable in controlling the direction of passage of a tracheal tube with both video assisted and direct laryngoscopy, especially when speed of tracheal intubation is important (as in emergency patients).5 Evidently, addressing this issue is useful for comparing the results obtained from this and previous studies.4,6–9
Fourth, haemodynamic and respiratory compromise are often present in patients requiring emergency intubation. Other than first-pass success, the time required for intubation is also of concern, especially in patients at risk of hypoxia or bronchoaspiration.10 Thus, in designing a study comparing the performance of devices for emergency intubation, it may be best to define a reasonable cut-off time for first-pass success.
Finally, improved laryngeal visualisation with the C-MAC videolaryngoscope did not translate into a higher first-attempt success rate in this study.1 We agree with Hossfeld et al.6 that the use of C-MAC videolaryngoscope as a first-line device for emergency intubation is a well tolerated procedure, as it provides various options: direct and video laryngoscopy can be performed with the same device and the video option is useful when difficult or failed direct laryngoscopy occurs during an emergency intubation.8,9
Acknowledgements related to this article
Assistance with the letter: none.
Financial support and sponsorship: none.
Conflicts of interest: none.
1. Sulser S, Ubmann D, Schlaepfer M, et al. C-MAC videolaryngoscope compared with direct laryngoscopy for rapid sequence intubation in an emergency department: a randomised clinical trial. Eur J Anaesthesiol
2. Niforopoulou P, Pantazopoulos I, Demestiha T, et al. Video-laryngoscopes in the adult airway management: a topical review of the literature. Acta Anaesthesiol Scand
3. Kelly FE, Cook TM. Seeing is believing: getting the best out of videolaryngoscopy. Br J Anaesth
2016; 117 (suppl 1):9–13.
4. Sakles JC, Mosier JM, Patanwala AE, et al. The utility of the C-MAC as a direct laryngoscope for intubation in the emergency department. J Emerg Med
5. Levitan RM, Heitz JW, Sweeney M, et al. The Complexities of tracheal intubation with direct laryngoscopy and alternative intubation devices. Ann Emerg Med
6. Hossfeld B, Frey K, Doerges V, et al. Improvement in glottic visualisation by using the C-MAC PM video laryngoscope as a first-line device for out-of-hospital emergency tracheal intubation: an observational study. Eur J Anaesthesiol
7. Sakles JC, Mosier J, Chiu S, et al. A comparison of the C-MAC video laryngoscope to the Macintosh direct laryngoscope for intubation in the emergency department. Ann Emerg Med
8. Vassiliadis J, Tzannes A, Hitos K, et al. Comparison of the C-MAC video laryngoscope with direct Macintosh laryngoscopy in the emergency department. Emerg Med Australas
9. Sakles JC, Mosier JM, Patanwala AE, et al. The C-MAC (video laryngoscope is superior to the direct laryngoscope for the rescue of failed first-attempt intubations in the emergency department. J Emerg Med
10. Natt BS, Malo J, Hypes CD, et al. Strategies to improve first attempt success at intubation in critically ill patients. Br J Anaesth
2016; 117 (suppl 1):i60–i68.