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Three Part Question

For [adult patients with airways deemed ‘difficult’ to intubate] is [video laryngoscopy a useful tool] within [the prehospital environment]?

Clinical Scenario

You are part of a HEMS crew and are called to a 53-year-old motorcyclist who is reported to be not breathing after a collision with another vehicle. Ambulance crews are already on scene and have commenced advanced life support. An iGel is in situe and you consider upgrading this to an endotracheal tube. You note however that the patient has a cervical collar fitted and that his airway sounds contaminated. You wonder if using a video laryngoscope will aid in your intubation of this patient.

Search Strategy

MEDLINE using the OVID interface, 2008-2019. [(“Prehospital” ti. AND “Video” ti. AND “intubation” af.)]. LIMIT to English Language. LIMIT to adaptive clinical trial OR case report OR clinical trial all OR comparative study OR controlled clinical trial OR observational study OR pragmatic clinical trial OR randomised controlled trial OR systematic review.
PUBMED, 2008-2019. [(“Prehospital” ti. AND “Video” ti. AND “Intubation” af.)]. LIMIT to English Language. LIMIT to adaptive clinical trial OR case report OR clinical trial all OR comparative study OR controlled clinical trial OR observational study OR pragmatic clinical trial OR randomised controlled trial OR systematic review.

Search Outcome

Medline and PubMed yielded 17 and 22 results respectively after combination of search terms and application of limitations. 10 duplications were found in the results and disregarded accordingly. 7 results were excluded as letters to journal editors while a further 8 were excluded as being not relevant to the problem presented. As such, 7 papers were left for analysis and critique.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Kreutziger, J., Hornung, S. and Harrer, C. et al (2019)	514 adult patients requiring emergency endotracheal intubation. “McGrath” Video Laryngoscopy (VL) or Direct Laryngoscopy (DL) used as 1st and 2nd attempt, then crossover if failed thereafter.	Randomised control trial.	Success rate of intubation using VL vs DL.	VL and DL success rate 98.1% and 98.5% respectively.	Study discontinued after interim analysis once half the number of patients had been enrolled, limiting its statistical power. Changes to personnel involved in the study due staff turnover may have affected results. Only one brand of VL compared against standard DL.
			Number of attempts / switches to achieve successful intubation	VL switched out 38 times vs. DL being switched out 27 times after 2 failed attempts.
			Measurement of degree of glottis visualisation.	Greater view of the glottis with the VL but higher risk of encountering technical problems.
Cooney, D., Beaudette,C. and Clemency, B. et al (2014)	Convenience sample of 81 ambulance personnel trained on using a new VL having only used DL prior to this. Each participant was asked to intubate a manikin using both the VL and standard DL techniques. The time to successful intubation was recorded.	Cohort study	Median total time for intubation.	Median total time for VL vs. DL was 15.5 seconds and 15.0 seconds respectively.	Extremely limited training on use of VL (8 minute video followed by 20 minute practice prior to the trial) may put accuracy of the data in doubt. Manikin-based and in a clinical environment. As a result, the study results may not be assimilate those seen in the prehospital arena. Varying experience of clinicians involved.
			Number of attempts required to successfully intubate the airway manikin.	First attempt intubation was achieved in 95.1% using DL and 96.3% using VL. 2.46% required 2 attempts at DL and 2.46% required 3 attempts. 2.46% required 2 attempts at VL and 1.23% required 3 attempts.
Yilidrim, A., Kiraz, H. and Agaoglu, I. et al (2016)	40 ambulance personnel were asked to perform intubations in three different manikin-based scenarios (normal airway / cervical collar / manual in-line stabilisation) using three different types of laryngoscope (VL / DL / McCoy). The pairing of scenario to blade type was randomised.	Randomised crossover study	Success rate of successful endotracheal intubation.	VL and McCoy success rate significantly higher (p<0.05) (100% vs. 90% respectively).	Simulation using manikins so data harvested has limited value. Participants had limited experience in the skill of intubation. Successful intubation defined at “completion within 75 seconds”, which is longer than ‘standard / recommended’ timings.
			Duration of intubation procedure.	Mean time taken to intubate using the VL significantly shorter than using standard DL or McCoy blade (p<0.001).
Aziz, M., Dillman, D. and Kirsch, J. et al (2009)	25 novice paramedic students randomised to intubate a stretcher-based manikin using either standard DL or VL. The students would then swap instruments and migrate to a second intubation scenario (either normal neck positioning or stiff-neck; whichever had not been completed prior). This was then repeated with a floor-based manikin.	Randomised crossover study.	Percentage of glottic opening (POGO) measured in the different scenarios.	VL improved POGO by 16% (+/-6%) (p<0.05) in the normal neck scenario and improved POGO by 33% (+/-7%) (p<0.05) in the stiffened neck scenario.	Simulation using manikins so data harvested has limited value. Confirmation of intubation success pre-hospital must include end-tidal CO2 readings, which is impossible in a manikin. Participants not blinded to the blade they would be using. Only one brand of VL blade compared to standard DL.
			Success rate of intubation.	Intubation success rate was equal using both forms of blade (94%).
			Intubation completion time.	Intubation timing was longer in some subgroups using the VL.
Eberlein, C., Luther, I. and Carpenter, T. (2019)	Data review of 296 patients intubated by ambulance staff either by DL or VL and brought to the ED. The first pass success rate was recorded.	Retrospective cohort study	Success rate of first-pass success rate.	Success rating using VL was 12.6% higher (85.6% vs. 73.0%) than DL.	Heights and weights of the patients were estimated and therefore attempted correlation of intubation success rate to these variables is weak. Data recorded was primarily for quality improvement purposes and therefore lacked depth. Varying experience of ambulance clinicians and thereby producing another uncontrolled variable. Furthermore the decision whether to use VL vs. DL was solely at the discretion of the staff member and not randomised, thus rendering the data liable to skewing.
			First pass rate measured against variables including age / weight / gender.	No correlation between number of attempts and variables stated.
Rhode, M., Vandborg, M. and Rognas, L. (2016).	Data review of 273 patients intubated by prehospital, physician-led, critical care teams in a 12 month period.	Observational study	First-pass success rate of intubation using the VL recorded and compared to Pre-VL data.	Overall first-pass success rate not statistically significant to pre-VL data (80.8% vs. 77.6%)(p=0.27).	Data recorded retrospectively (post-incident) and therefore subject to recall bias. Implementation of SOP’s and pre-intubation / RSI checklists mid-way through the study grossly affected the results and arguably is the sole reason for improved success rates.
			Final 9 months of data analysed separately (after the implementation of a Standard operating procedure (SOP) and Check-list).	Overall first-pass success rate was 80.1% however post-RSI success rate increased to 94.4%.

Comment(s)

It is widely accepted that endotracheal intubation is ‘Gold Standard’ in terms of airway management and is a skill that is bestowed upon anaesthetists, emergency physicians and paramedics alike. In the prehospital setting, clinicians can expect to encounter patients that present with ‘difficult’ airways, which Bjoernsen and Lindsay (2008) state can be defined by “the requirement of multiple attempts with standard Macintosh laryngoscope blade or impossible visualisation of the glottis”. In an effort to increase the rate of successful first-pass intubation rates, some prehospital care providers have opted to introduce video laryngoscopes (VL) and yet little research has been produced to validate their efficacy. Cooney, Beaudette and Clemency et al. (2014) trained 81 qualified ambulance personnel on a new VL having only used direct laryngoscopy (DL) prior to this. Each participant was asked to intubate a manikin using both the VL and standard DL techniques. The number of attempts, as well as the time to successful intubation were recorded. Whilst the VL did not statistically improve or worsen the success rate (in terms of number of attempts required), it did prove to be quicker from start to finish (5.5 seconds on average). It is worth remembering however that as this study was conducted on manikins, it arguably has limited relevance to ‘real life’ airways. It was also noted that the participants had varying degrees of clinical experience, leaving the data open to skewing. The same issues could be found in the study by Yilidrim, Kiraz and Agaoglu et al. (2016), in which 40 ambulance personnel (with varying lengths of service) were randomised to intubate a manikin with differing degrees of neck rigidity, using a variety of laryngoscopes. This study found that VL did actually improve intubation success rates and gave a shorter time from blade introduction to passage of the tube. A major flaw noted in this study however was that successful intubation was defined as completion within 75 seconds, which is far greater than recommended timings, according to the Difficult Airway Society (DAS). Addressing the issue of varying clinical experience, Aziz, Dillman and Kirsch et al. (2009) randomised 25 novice paramedic students to intubate a manikin in a range of positions with varying degrees of neck ‘stiffness’, utilising either DL or VL. This study found that the VL did not improve success rates of intubation and in fact increased intubation times in some subgroups. That said, percentage of glottic opening (POGO) was increased substantially; 16% in the ‘normal’ and 33% in the ‘stiff-necked’ manikin. Similar to the study presented above, it could be argued again that the data harvested by this study is of limited value with it being manikin-based and whilst the participants were randomly matched to their intubation instrument, they were not blinded prior to the study. Eberlein, Luther and Carter (2019) analysed data of 296 real patients who had been intubated by emergency medical services (EMS) prehospitally, either by DL or VL, concluding that first-pass success rates were statistically improved using a VL over DL (85.6% vs. 73%). However, the evidence produced by this retrospective review had profound limitations, particularly as the data was input originally for the purposes of a separate quality-control project and therefore lacked depth. Clinicians were not part of a study cohort and therefore their decision to use either VL or DL was subjective whilst their record keeping was retrospective. As a result, it could be argued again that the data was liable to skewing. Similarly the observational study by Rhode, Vandborg and Rognas (2016), which had initially shown no statistical improvement of intubation success rate using a VL, was also prone to skewing of the data: 3 months into the study new standard operating procedures (including the use of pre-RSI checklists) were introduced, seeing a massive increase in the first-pass success rate of both DL and VL. A well-established, randomised clinical trial (RCT) was conducted by Trimmel, Kreutziger and Fitzka et al. (2016) this time studying physician-led, prehospital critical care teams and their success rates using DL or VL in the form of the ‘Glidescope’. 326 patients were recruited into the study whilst physicians were randomised to use either DL or the Glidescope VL before swapping if their first two attempts failed. In this scenario DL had a far higher first-pass success rate (96.2% vs. 61.9%) than the Glidescope VL, although it was noted that the VL was successful in ‘bailing out’ 67% of previous failed DL attempts. Kreutziger, Hornung and Harrer (2019) repeated this RCT, this time using a different brand of VL known as the ‘McGrath’ and found the results to be astonishingly different; first-pass success rates were 98.1% and 98.5% for VL vs. DL in the 514 patients recruited into the study. Patients requiring a switch to an alternate device were also regarded as low. Of course both studies were not without limitations, namely varying degrees of experience and specialty of the physicians while the latter of the studies was halted part way through, limiting its statistical power.

Clinical Bottom Line

The use of a video laryngoscope, whilst not directly improving the first-pass success rate of intubation for experienced clinicians, may still prove to be a useful support tool for use in those patients deemed to possess features predictive of difficult airways, particularly for those clinicians with less experience. It has also been shown to be a useful back-up tool for failed first attempts at direct laryngoscopy. Video laryngoscopes are inherently susceptible to technical problems such as camera misting or soiling and as a result, direct laryngoscopy must be retained as a primary skill. Different techniques of intubation do not negate the importance of check-lists and standard operating procedures.

References

1. Helmut Trimmel, MD; Janett Kreutziger, MD; Robert Fitzka, MD; Stephan Szüts, MD; Christoph Derdak, MD; Elisabeth Koch, MD; Boris Erwied, MD; Wolfgang G. Voelckel, MD Use of the GlideScope Ranger Video Laryngoscope for Emergency Intubation in the Prehospital Setting: A Randomized Control Trial* Society of Critical Care Medicine and Wolters Kluwer Health, Inc. July 2016 • Volume 44 • Number 7
2. Janett Kreutziger, MD, PhD; Sonja Hornung, MD; Clemens Harrer, MD; Wilhelm Urschl, MD; Reinhard Doppler, MD; Wolfgang G. Voelckel, MD, MSc, PhD; Helmut Trimmel, MD, PhD, MSc Comparing the McGrath Mac Video Laryngoscope and Direct Laryngoscopy for Prehospital Emergency Intubation in Air Rescue Patients: A Multicenter, Randomized, Controlled Trial Journal of Critical Care Medicine October 2019 • Volume 47 • Number 10
3. Derek R Cooney , Charles Beaudette , Brian M Clemency , Christopher Tanski and Susan Wojcik Endotracheal intubation with a video-assisted semi-rigid fiberoptic stylet by prehospital providers Springer & International Journal of Emergency Medicine 2014, 7:45
4. Ahmet Yildirim, Hasan A. Kiraz, Ibrahim Agaoglu, Okhan Akdur. Comparison of Macintosh, McCoy and C-MAC D-Blade video laryngoscope intubation by prehospital emergency health workers: a simulation study Springer & Intern Emerg Med (2017) 12:91–97
5. Michael Aziz, Dawn Dillman, Jeffrey R. Kirsch & Ansgar Brambrink Video Laryngoscopy with the Macintosh Video Laryngoscope in Simulated Prehospital Scenarios by Paramedic Students Taylor & Francis - Prehospital Emergency Care April-June 13 / 2
6. Eberlein, C., Luther, S., Carpenter, T. and Ramirez, L. (2019) First-Pass Success Intubations Using Video Laryngoscopy Versus Direct Laryngoscopy: A Retrospective Prehospital Ambulance Service Study. Elsevier & Air Medical Journal Associates 2019 Sep - Oct;38(5):356-358.
7. Marianne Grønnebæk Rhode , Mads Partridge Vandborg , Vibeke Bladt and Leif Rognås Video laryngoscopy in pre-hospital critical care – a quality improvement study BioMed Central & Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2016) 24:84