Direct vs Video Laryngoscopy
In 1878 William MacEwan first passed a tube into the trachea of an awake patient using his fingers as a guide. Now health care providers routinely perform endotracheal intubation as a life saving intervention. Despite over 100 years of experience, this procedure is still associated with significant risk, especially for novice and low volume intubators. Many tools have been developed to mitigate the risk of not securing an airway, including intermediate airway devices such as the Combitube and laryngeal mask airway and airway adjuncts such as the Eschmann stylet. In recent years, video laryngoscopes have made their way into emergency departments and intensive care units. Do these devices offer a better view of the larynx? Do they increase the chance of successful intubation in routine cases? What about difficult airways? Is one video laryngoscope better than the rest? A flurry of investigations in the last decade have attempted to sort through these important issues.
In 2009, Brown et al showed that good glottic views improved from 80% to 93% by using a video Macintosh larygoscope in routine emergency room patients [1]. Subsequently, Ayoub et al randomized 42 medical students to Macintosh vs Glidescope facilitated intubation training on manikins and then showed a significant improvement in first pass success rates on actual patients when using the Glidescope [2]. Patients predicted to have difficult airways were excluded from this study. For such patients, there is a paucity of randomized trials comparing direct laryngoscopy to video laryngoscopy outside of the operating room. Some data suggests video laryngoscopy, when used for predicted difficult airways, reduces force on maxillary incisors [3] and causes less cervical spine movement in trauma patients [4]. A potential disadvantage of video laryngoscopy is a longer time to tracheal intubation [5], although this has not been shown to be true with all devices and probably improves as intubators gain more experience with indirect laryngoscopy.
Since their introduction over a decade ago, several video laryngoscopes have been developed, and their manufacturers have engaged in fierce competition to demonstrate superiority. Several head to head comparisons have evaluated different devices [6] [7] [8] [9]. Among non-industry sponsored studies, no video laryngoscope has risen to the top as clearly superior. However, each has distinct advantages. For example, the Glidescope comes in pediatric sizes that can be used in adults with limited interincisor opening. The Storz V-Mac uses a traditional Macintosh blade that provides a straighter trajectory to the glottis when compared to the Glidescope and McGrath. These have steeply angulated blades requiring the use of specialized stylets. The integrated tube channel of the Pentax Airway Scope may facilitate more rapid intubation compared to other devices.
In my own practice in emergency and critical care medicine, I mostly supervise as residents secure the airway. In these settings, I ask residents to start with direct laryngoscopy. In response to their complaints, I point out that electronic equipment sometimes fails and that they may someday practice in a facility that does not own a video laryngoscope. For trauma patients with cervical immobilization, I start with video laryngoscopy to decrease the risk of cervical motion. In patients with predicted difficult airways, I have the video laryngoscope set up and turned on but start with direct laryngoscopy. In this setting, the video laryngoscope serves as a backup parachute that is sometimes needed to help land with a secure airway.
References:
[1] Brown CA III et al. Improved glottic exposure with the video Macintosh laryngoscope in adult emergency department tracheal intubations. Ann Emerg Med 2010 Aug; 56:83. Link.
[2] Ayoub CM et al. Tracheal intubation following training with the GlideScope® compared to direct laryngoscopy. Anaesthesia 2010 Jul; 65:674. Link.
[3] Lee RA et al. Forces applied to the maxillary incisors during video-assisted intubation. Anesth Analg 2009 Jan; 108:187. Link.
[4] Robitaille A et al. Cervical spine motion during tracheal intubation with manual in-line stabilization: Direct laryngoscopy versus GlideScope® videolaryngoscopy. Anesth Analg 2008 Mar; 106:935. Link.
[5] Walker L et al. Randomized controlled trial of intubation with the McGrath® Series 5 videolaryngoscope by inexperienced anaesthethists. Br J Anaesth 2009 Sep; 103:440. Link.
[6] Maassen R et al. A comparison of three videolaryngoscopes: The Macintosh laryngoscope blade reduces, but does not replace, routine stylet use for intubation in morbidly obese patients. Anesth Analg 2009 Nov; 109:1560. Link.
[7] Liu L et al. Tracheal intubation of a difficult airway using Airway Scope, Airtraq, and Macintosh laryngoscope: A comparative manikin study of inexperienced personnel. Anesth Analg 2010 Apr; 110:1049. Link.
[8] van Zundert A et al. A Macintosh laryngoscope blade for videolaryngoscopy reduces stylet use in patients with normal airways. Anesth Analg 2009 Sep; 109:825. Link.
[9] Liu EHC et al. Tracheal intubation with videolaryngoscopes in patients with cervical spine immobilization: A randomized trial of the Airway Scope® and the GlideScope®. Br J Anaesth 2009 Jun 19; [e-pub ahead of print]. Link.