The Trip Report: Direct vs. Video Laryngoscopy

The Trip Report: Direct vs. Video Laryngoscopy

Which proved to be fastest for providers wearing Level C protective gear?

Reviewed this Month

Airway Management in Disaster Response: A Manikin Study Comparing Direct and Video Laryngoscopy for Endotracheal Intubation by Prehospital Providers in Level C Personal Protective Equipment.

Authors: Yousif S, Machan JT, Alaska Y, Suner S. 
Published in: Prehosp Disaster Med, 2017
Mar 20; 32(4): 1–5.

This month is dedicated to EMS disaster response research. This is a very well-done study that examines performance in airway management when using two types of video laryngoscopy devices and direct laryngoscopy using a Macintosh blade. For this experiment EMS providers wore Level C PPE. Previous studies have demonstrated that airway management while wearing PPE is associated with increased time to control the airway and decreased success rates.

With the increased popularity of video laryngoscopy in the field, studies examining its use in a variety of situations are definitely needed. Further, understanding whether this tool can help EMS providers’ performance during an already-stressful situation is absolutely an important addition to the literature. This study design was great for examining their research questions. This was a prospective, randomized crossover study. Prospective is very important here: This means they developed the experiment and data collection plan prior to performing the study. While retrospective studies can often answer important questions, prospective studies are more scientifically rigorous. The investigators also randomized the order that each EMS provider performed the intubations using the Macintosh blade and either Verathon’s GlideScope Ranger (with unmounted screen) or King Systems’ King Vision video laryngoscope. The crossover part indicates that each EMS provider “crossed over” and used each of the interventions at least once. The outcome of interest chosen by the investigators was the time it took to intubate (or fail to intubate) and provider satisfaction with the device. 

The experiment was performed in a controlled environment. All intubations were performed on a Resusci Anne manikin. A convenience sample of 20 EMS providers participated. We have mentioned convenience samples previously; that just means the authors didn’t try to include EMS providers who might mirror the national EMS workforce. The EMS providers in this study were from one agency and all had at least two years’ experience in airway management, as well as medical clearance to use respiratory protection equipment. There were 18 paramedics. All but one of the participants was male, and their average age was 41. One interesting thing about this convenience sample was that all of them had ample experience with a Macintosh blade but little to no experience with video laryngoscopy. 

We recently reviewed a pilot study with a small number of participants. This study also lacks a huge number of participants, but the investigators did some up-front work to determine the number needed to appropriately evaluate the results. In other words, they performed a sample size calculation that determined their study could detect a statistically significant difference in the time to intubation. The authors predefined a significant difference for this study as more than 16 seconds. This predefined difference is key to determining the number of participants needed. The bigger the difference, the fewer participants needed, and the smaller the difference, the more participants needed. 

The authors also used appropriate statistical tests to evaluate the results. They even made some statistical adjustments in the analysis to reduce the chance of mistakenly claiming an intervention was effective. This adjustment is needed for many clinical trials; it’s called adjusting for multiplicity. 

All the above shows that the authors took the analysis seriously from the start. They did a lot of things right, which should strengthen our confidence in their results. 


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Let’s get to the results: When evaluating time to intubation, the Macintosh laryngoscope performed the best, with an average time of 25.69 seconds. The King Vision performed second best, with an average time of 29.87 seconds. The GlideScope Ranger had an average time to intubation of 35.82 seconds. 

The second outcome of interest was the EMS providers’ satisfaction with each device. Interestingly, these results did not align with what we might expect given the time-to-intubation results. The EMS providers were most satisfied with the King Vision, at 86.7%. Next best in terms of satisfaction was the GlideScope Ranger with 73.0%. Finally, the Macintosh satisfied 69.9% of participants.

Clearly these providers are embracing technology. Even though the GlideScope Ranger was associated with the slowest time to intubation, EMS users were more satisfied with it than with the Macintosh blade, which was associated with the shortest time to intubation. Remember that the participants regularly used the Macintosh for field intubations but never used video laryngoscopes. We might expect them to be quicker with a tool they regularly use. It would be interesting to see this study performed with at least some EMS providers who regularly use video laryngoscopy. 

One thing the authors did not list as an outcome of interest was the percentage of successful intubations. Interestingly, the only failure was associated with use of the Macintosh. Both video laryngoscopes were 100% successful. The authors couldn’t discuss this in depth because it was not one of their predefined outcomes of interest, so technically their study was not designed to evaluate it. However, this is where the subject matter expertise of the EMS providers reading this manuscript really matters. While the study was not specifically designed to evaluate success, the fact that the only failure was associated with the Macintosh is still an important result. This result is even more relevant when we remember that the participants had never previously used video laryngoscopes but regularly used the Macintosh. This just helps prove that no matter how hard authors work to design a great study, no study is perfect. 


This study seems to support that the use of video laryngoscopy during a disaster response may be a valuable tool to assist EMS providers in delivering the best care possible in a very stressful environment. The authors here put together a well-designed study that provides some very important information. The strengths and compelling results of this study make it easy to want to accept the results without further investigation; however, we should remember that this was a convenience sample. It would be interesting to see a more diverse group of EMS providers used in the same experiment.  

Antonio R. Fernandez, PhD, NRP, FAHA, is research director at the EMS Performance Improvement Center and an assistant professor in the Department of Emergency Medicine at the University of North Carolina–Chapel Hill. He has been a nationally certified paramedic since 2005 and completed the EMS Research Fellowship at the National Registry of Emergency Medical Technicians.


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