MSM 010 Is Video Laryngoscopy superior to direct laryngoscopy?

“If you don’t have control of the airway, you don’t have control of anything.”

-Numerous EMS instructors everywhere

            There is a debate that has been hotly contested in EMS and emergency medicine for almost a decade or so now, and it pertains to the best way to maintain an airway for a patient that cannot do it themselves. The advent of rapid sequence induction and the cultural shift in favor of using Ketamine as an induction agent has led to further discussion about which tools we should use to properly intubate. Since paramedics began developing and learning the skill of intubating in the field we have made significant progress from only intubating cardiac arrest patients, to introducing a significant number of benzodiazepines to sedate the patient sufficiently to intubate them, and now we are in the modern era of RSI. Until recently, these interventions involved using direct laryngoscopy, or using a laryngoscope to directly visualize the patient’s vocal chords and passing an ET tube through the opening. As time and medical science has evolved, EMS has finally caught up and has begun using video laryngoscopy to attain airway management. The on-going debate that exists in the EMS culture is which method is preferred. Perhaps we should use VL for RSI patients, and DL for cardiac arrest patients? What about difficult airways in general? Of course, we also have the “old school” mentality of “I can intubate anyone with a MAC 4” which is, at most, anecdotal.

The debate surrounding pre-hospital intubation is one that is not unfounded. Specifically, there is a risk of skills attrition for providers that do not perform the skill often enough. Projects that are flush with medics will not see significant numbers of paramedics intubating, and still other projects have their superstar intubators who will be the only member of a team that perform the procedure, thus leading to all other team members losing the skill. Beyond that, there is some data to suggest that up to 31% of intubation attempts are failed.[1] However, this number was not significantly associated with an increase in mortality. We also know that early and successful intubation for trauma patients is associated with decreased mortality[2]. Adding to the discourse is a study from 2011 that showed that nationwide, the success rate of intubation is 77%[3]. So, it seems clear that we have some work to do when it comes to managing airways.

Direct laryngoscopy carries many variables that are simply beyond our control. Patients that have difficult airways, or obscure airway anatomy can prove problematic for successful intubation, as well as physical factors of the provider that is performing the skill. If a paramedic or physician does not have adequate forearm strength to properly displace the prominent structures of the patient’s airway to visualize the vocal chords, clearly no successful intubation can be performed. This is not to speak of trauma patients that have experienced significant injuries to the face or to the trachea. There is a lot to explore.

In 2016, the Cochrane Library (The data source for all my stats heads out there) performed a meta-analysis examining endotracheal intubation and their success rates. They pulled 64 studies from 2015 that involved a total of 7044 patients. The studies were diverse and analyzed retrospective human studies, simulated difficult airway studies, and studies that analyzed patients that did not have anticipated difficult airways. As one may expect, Cochrane found that the use of VL (VAL as they refer to it) resulted in less failed intubation attempts when a patient had an anticipated difficult airway[4]. This result is something that may be easily replicated, but may also be due in part to protocol development. If a provider or a project has VL available to them, and the protocol that they follow is designed to use VL for patients with anticipated difficult airways, one could easily imagine that more successful intubations would be achieved. However, there was no statistically significant difference in first-pass success between VL and DL. Cochrane also did not find any significant difference in hypoxia in either group. It is important to note that Cochrane performed a meta-analysis, which is a very high bar for research, and the data analyzed in the review included randomized control trials, quasi-randomized trials, and included parallel and cross-over designs. What about individual studies? Surely there are other RCTs out there that Cochrane did not include in their data. After all, Cochrane’s analysis covered only the year 2015. Perhaps this was an unusually successful year for intubations.

In 2015, a group of critical care fellows in New York performed an RCT using 117 patients in a controlled environment comparing the use of a GlideScope to direct laryngoscopy. Patients we randomized to one group or another by a simple selection process. First-pass success rate was almost double in the VL group compared to the DL. Perhaps more importantly, the amount of times that more than two attempts were required with DL was 3 times as much as with VL, and the amount of time required to successfully intubate with DL was almost twice that of VL. This study shows compelling evidence for the use of VL over DL, however as with any data set, the study has its limitations. Namely, patients that were receiving an elective procedure, had a known history of difficult intubations, any limit to the size of the airway (e.g. angioedema, oropharyngeal masses), or an oxygen saturation of less than 92% were excluded from the study.

In 2016, the Mayo clinic in Minnesota analyzed their own candidates for intubation, specifically those that required airway control secondary to sepsis[5]. Approximately one-third of these patients had the additional complication of obesity. The patients in this study may translate more appropriately to EMS and emergency medicine as most patients were sedated with etomidate and paralyzed with rocuronium or succinylcholine. Mayo found that there was no significant difference in first-pass success rates, and no significant difference in the rate of successful airway control. To be clear, the mean first-pass success rate was 67.35%. However, despite the questionably low first-pass success rate, Mayo found no significant difference between the study groups in time to intubation, percent change of oxygen saturation, duration of mechanical ventilation, length of stay, or mortality.

To further muddy the waters, a recent JAMA publication includes an RCT from France analyzing VL versus DL in ICU patients requiring intubation[6]. The design of the study is among the more solid that seem to be available in the literature. 371 patients were randomized into a group of 186, and a group of 185. The primary practitioners that performed the skills were considered “non-experts” (read: residents), and the outcomes were successful first-pass attempts, and time to intubation was a secondary outcome. The patients that were involved in the study also performed a 28-day follow-up, an element in the study that is not found in much of the other literature. The French physicians found that VL did not improve first-pass success, and in fact was associated with higher rates of severe life-threatening complications.

So where does this leave us? Analysis of the available data shows one consensus consistently, and that is that VL improves the glottic view when performing an intubation. It is not convincing that this is up for debate. Cameras tend to see things more clearly than our eyes do. However, that seems to be the only thing that the data can agree on. We see many studies that show improved airway control with VL, but those studies tend to omit what may be significant data, or exclude patients that would potentially skew the data toward failure. The Mayo study seems to correlate more significantly to EMS use than the rest of them, given the use of pharmacologic intervention. However, as with most studies, Mayo concludes that more research is required to adequately make a judgement as to which technique is best. Given the universal improvement of the glottic view, VL may be preferable for EMS in the setting of RSI or anticipated difficult airways. Patients that have significant facial trauma may also be good candidates to consider for VL. Beyond that, it seems the data is still our as to which technique is “best” for EMS. A broad, multi-center RCT involving EMS agencies is needed. When that occurs, we may have a better idea of what works in our field. Until then, it seems the jury is still out in the VL vs DL debate.

[1] Prehospital intubations and mortality: a level 1 trauma center perspective.

Cobas MA, De la Peña MA, Manning R, Candiotti K, Varon AJ

Anesth Analg. 2009 Aug; 109(2):489-93.

[2] Timing is everything: delayed intubation is associated with increased mortality in initially stable trauma patients.

Miraflor E, Chuang K, Miranda MA, Dryden W, Yeung L, Strumwasser A, Victorino GP

J Surg Res. 2011 Oct; 170(2):286-90.

[3] Out-of-hospital airway management in the United States.

Wang HE, Mann NC, Mears G, Jacobson K, Yealy DM

Resuscitation. 2011 Apr; 82(4):378-85

[4] Lewis SR, Butler AR, Parker J, Cook TM, Smith AF. Videolaryngoscopy versus direct laryngoscopy for adult patients requiring tracheal intubation. Cochrane Database of Systematic Reviews 2016, Issue 11. Art. No.: CD011136. DOI: 10.1002/14651858.CD011136.pub2

[5] Janz DR, Semler MW, Lentz RJ, et al. Randomized trial of video laryngoscopy for endotracheal intubation of critically ill adults. Crit Care Med 2016;44:1980-1987

[6] Lascarrou, et al Video Laryngoscopy vs Direct Laryngoscopy on Successful First-Pass Orotracheal Intubation Among ICU Patients
A Randomized Clinical Trial JAMA. 2017;317(5):483-493. doi:10.1001/jama.2016.20603

Image credit: Emergency Physicians Monthly