We read with great interest the comments of Liu et al. about our study ‘Success rates and endotracheal tube insertion times of experienced emergency physicians using five video laryngoscopes: a randomised trial in a simulated trapped car accident victim’.1 We appreciate the interest in our work and are grateful for the chance to comment on the topics raised by Liu et al.2
Our study was intentionally designed in a way that places the physician in a very uncommon situation for managing tracheal intubation. Tracheal intubation sometimes has to be performed in difficult circumstances and uncommon positions in pre-hospital emergency medicine.3,4 As these situations are very rare, they cannot be sufficiently practiced. Therefore, practical experience is very limited, even for highly experienced emergency physicians. Furthermore, the number of intubations performed, in German pre-hospital emergency medicine, is limited (approximately one tracheal intubation every 55 to 213 days).5
To further explain the background of the study, specific knowledge of the physician-based German Emergency Medical System is required. In Germany, the vehicles and helicopters of Emergency Medical System have standardised equipment (e.g. laryngoscope with Macintosh blades size 0 to 5). However, a great variety of supplementary equipment for airway management, such as laryngeal tubes, laryngeal masks, indirect or video laryngscopes, may be found.6–8 Thus, an emergency physician on call may regularly find himself with different equipment at different ambulance stations.9 The physician must, therefore, be familiar with the handling of all devices, and standardised instruction has to be obtained for all medical products prior to their first use. But, the use of these devices cannot be extensively practiced. Learning curves, especially for video laryngoscopes, are steep. However, we wanted to test the performance in an unknown situation such as may occur on any Emergency Medical System mission when the physician has limited experience with that device (despite being a specialist in airway management).
All participants had regular experience (>25 times) with one and occasional experience (>5 times) with another of the tested video laryngoscopes for in-hospital management of both expected und unexpected difficult airways. This means that, in theory, there could be a bias – as Liu et al. suggest. Surprisingly, the video laryngoscope which was familiar to the participants did not perform better than the devices that were new to them. We hypothesise that learning curves do not start at ‘zero’ when using unknown devices in an untrained situation. However, we have not investigated this specific point.
We also thank Liu et al. for their important point that the Airtraq should correctly be titled an ‘indirect optical laryngoscope’ instead of video laryngoscope. However, in contrast to the Macintosh, it facilitates an indirect view of the glottis which is the main principle of video laryngoscopes and why we used it in the same group.
Assistance with the study: none declared.
Sources of funding: none declared.
Conflicts of interest: none declared.
1. Wetsch WA, Carlitscheck M, Spelten O, et al. Success rates and endotracheal tube insertion times of experienced emergency physicians using five video laryngoscopes: a randomised trial in a simulated trapped car accident victim. Eur J Anaesthesiol
2. Liu K-P, Cheng Y, Xue FS, Li R-P. Rational comparison of tracheal intubation with direct and indirect laryngoscopes in a simulated trapped manikin. Eur J Anaesthesiol
3. Koetter KP, Hilker T, Genzwuerker HV, et al. A randomized comparison of rescuer positions for intubation on the ground. Prehosp Emerg Care
4. Koetter KP, Maleck WH. Reference for ice-pick position for intubation. Prehosp Emerg Care
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7. Schmid M, Schüttler J, Ey K, et al. Equipment for prehospital airway management on Helicopter Emergency Medical System helicopters in central Europe. Acta Anaesthesiol Scand
8. Genzwürker H, Lessing P, Ellinger K, et al. Infrastructure of emergency medical services. Comparison of physician-staffed ambulance equipment in the state of Baden-Wuerttemberg in 2001 and 2005. Anaesthesist
9. Schmidt U, Eikermann M. Organizational aspects of difficult airway management: think globally, act locally. Anesthesiology