Tales are often told of an exhausted travel who has lost their way in the desert, and are drawn astray by the the sight of a lush oasis. But as they draw close, their salvation vanishes only to reappear on the distant horizon. This optical tormentor continues to lead the hapless travelers further and further off course, until they collapse from sheer exhaustion. Such is the fallacy of the video laryngoscope. Or at least so it appears…
Published in JAMA, Lascarrou et al examined the efficacy of video laryngoscopy when compared to a traditional direct approach in patients requiring endotracheal intubation in 7 ICUs across France. The MACMAN trial randomized patients to either a first attempt using the standard geometry McGrath Mac Video laryngoscope vs a traditional Macintosh blade. Randomization was stratified by center and the experience level of the intubator performing the procedure. The authors utilized a strict protocol in an attempt to control for variations in practice that could potentially bias the results (variations in pre-oxygenations techniques, induction medication, etc.). An intubation attempt was defined from the time the laryngoscope blade was inserted into the patient’s oral cavity until the blade was removed. Successful intubation required confirmation using a waveform end-tidal CO2 monitor.
371 patients were randomized and included in the intention to treat analysis. The authors found no difference in their primary outcome, the rate of first pass success, between the two groups. 67.7% of the patients randomized to the video laryngoscopy group were intubated successfully on the first attempt compared to 70.3% of the patients in the direct laryngoscopy group. Nor did they find a difference in the number or duration of intubation attempts or the frequency of difficult intubation. The authors did note a concerning statistically significant increase in the number of severe life-threatening complications that occurred in the patients who underwent intubation using the video laryngoscope (9.5% vs 2.8%).
In addition, this study highlights the fallacy of video laryngoscopy. I am sure we have all felt the utter frustration of having a beautiful view of the vocal cords displayed on our high resolution screen only to watch our tube slip just below the interarytenoid notch over and over again. Lascarrou et al kindly demonstrated that we are not alone in this frustration. In fact, this shared vexation is quite commonplace. The video laryngoscope far outperformed its traditional brethren when it came to visualization of the vocal cords. Cormack-Lehane grade 1 views were achieved in 75.6% of the patient in the video laryngoscope group. This optimal view was only achieved in 52.5% of the patients who underwent direct laryngoscope. And while the rate of first pass failure was clinically identical between the two groups, how each group failed differed significantly. The primary reason for failure in patients who were randomized to receive direct laryngoscope was failure to visualize the glottis (70.6%). In contrast to the video laryngoscope group, the primary reason of failure was inability to pass the tube (70.7%). The study protocol prohibited intubators from utilizing an intubating stylet during their first attempt. This may have contributed to the failure rate when using the video laryngoscope and likely explains the increased use of the gum elastic bougie on first attempt (12% vs 5.5%). This is not a novel phenomenon, multiple studies have demonstrated while video laryngoscopy enhances glottic visualization, it does not improve clinically important outcomes (2,3,4,5). In fact, Gu et al found that a more limited view when using a hyperangulated video laryngoscope led to improved rates of success when compared to what is considered the ideal visualization of the glottic structures. Unfortunately, Lascarrou et al did not decipher the types of patients in which each of these respective modalities fail. Did these modalities fail in the same patients or does one device suffer where another may succeed? Perhaps we should tailor our blade selection to the specific anatomical and physiological challenges presented by the patient in front of us.
Despite my old fashioned love of the traditional direct laryngoscope, this study underestimates the true utility of a standard geometry video laryngoscope as it functions as both a direct and indirect laryngoscope in parallel rather in series. I imagine that if intubators were allowed to transition from an indirect view to a direct view of the glottis and vice versa when either failed, the video laryngoscope group would have appeared far more favorable. Though to be fair this is nothing more than conjecture.
Though this paper certainly has its limitations, it does highlight a number of key points. First, neither of these methods are perfect. When employed by inexperienced hands, both direct and video laryngoscopy will fail frequently. More importantly, this data set should remind us that when it comes to the airway, experience reigns supreme. The expert intubators far outperformed their less experienced peers (91.7% vs 64.6%), independent of the type of blade they used during the intubation. Video laryngoscopy does not simplify airway management, rather it changes the perspective. Reminding us while vivid and often gruesome images of the airway may appear advantageous, glottic visualization does not necessarily translate into successful intubation. Like the weary traveler, chasing the ever retreating mirage, at times its path does not always lead to salvation.
- Lascarrou JB, Boisrame-Helms J, Bailly A, et al; Clinical Research in Intensive Care and Sepsis (CRICS) Group. Video laryngoscopy vs direct laryngoscopy on successful first-pass orotracheal intubation among ICU patients: a randomized clinical trial. JAMA.
- Griesdale DE, Chau A, Isac G, et al; Canadian Critical Care Trials Group. Video-laryngoscopy versus direct laryngoscopy in critically ill patients: a pilot randomized trial. Can J Anaesth. 2012;59(11): 1032-1039.
- 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(11):1980-1987.
- Yeatts DJ, Dutton RP, Hu PF, et al. Effect of video laryngoscopy on trauma patient survival: a randomized controlled trial.J Trauma Acute Care Surg. 2013;75(2):212-219.
- Driver BE, Prekker ME, Moore JC, Schick AL, Reardon RF, Miner JR. Direct Versus Video Laryngoscopy Using the C-MAC for Tracheal Intubation in the Emergency Department, a Randomized Controlled Trial. Acad Emerg Med. 2016;23(4):433-9.
- Gu Y, Robert J, Kovacs G, et al. A deliberately restricted laryngeal view with the GlideScope® video laryngoscope is associated with faster and easier tracheal intubation when compared with a full glottic view: a randomized clinical trial. Can J Anaesth. 2016;63(8):928-37.