In our last article we discussed the use of channeled optical and video laryngoscopes to obtain improved glottic views and increase intubation success rates. This month we are going to look at non-channeled video laryngoscopes and how they can improve intubation success rates, particularly in the predicted difficult airway patients. Our two representative, but non-exclusive, devices are the Verathon® GlideScope Ranger and the McGRATH® Series 5 video laryngoscopes.
The GlideScope GVL produced by Verathon Inc. was first described in the literature in early 2003 as an alternative indirect video laryngoscope for intubation of the predicted difficult airway patient by Agro, et el. Since that time the GlideScope line of indirect laryngoscopes has evolved and the GlideScope Ranger is their primary model marketed for EMS use. Each videoscope utilizes a rigid, disposable or non-disposable stat positioned around the base of the tongue with the tip placed at the vallecula. A video screen connected by a protected cable to the stat then displays a video image of the structures visualized within the patient’s posterior pharynx. Once visualization of the glottis is obtained, a styletted endotracheal tube—using either the proprietary GlideRite® stylet, or any other stylet that is shaped similarly—is placed into the corner of the patient’s mouth under direct visualization. The tube is advanced into the posterior pharynx and rotated so the tip of the tube just disappears behind the tongue. The clinician then returns their view to the video monitor, identifies the tip of the ETT with only minor manipulation of the stylet if necessary, and then advances the tube tip under video visualization to the entrance of the glottis. The ETT is then advanced carefully off from the stylet and gently into the glottis, and positioned at an appropriate depth for the patient. The stylet is removed, followed by the stat, and the ETT is secured and utilized per normal fashion. This approach is comparable to other similar video laryngoscopes such as the KARL STORZ® C-MAC.
Success using this the GlideScope has been demonstrated by a number of different studies and with a wide variance of clinical experience. In the Armstrong, et el study published in the June 2010 Anaesthesia, the success of visualization of the glottis was measured in pediatric patients with known difficult or failed airways prior. After generalized induction the experienced clinician performed direct laryngoscopy (DL) with a standard blade, recording the laryngoscopes’ view and the time to obtain this view. The clinician then switched to the GlideScope and performed indirect laryngoscopy recording the same parameters. The study found there was a significant improvement in the laryngoscope view with the GlideScope compared to DL. Time difference to obtain the view between the devices was not significant. This study showed a clear advantage of the video laryngoscope in comparison to DL for the experienced provider in laryngoscope view.
Since EMS involves patients who are not always in optimum positioning for airway management, a study completed by Nakstad & Sandberg in 2009 compared the GlideScope® Ranger versus the standard Macintosh blades in simulated patients positioned in two different positions. The first scenario provided the manikin in an unrestricted access position in an ambulance. All clinicians successfully intubated the manikin utilizing both the GlideScope Ranger and traditional DL. In the second scenario the manikin was positioned with no access from the head-end, as might occur with an entrapped patient. All clinicians attempted intubation of the manikin in this position. Surprisingly, only 50% succeeded in endotracheal intubation with standard DL, while 100% of the clinicians were successful with use of the GlideScope Ranger. This study clearly demonstrates the GlideScope Ranger is superior to DL in the access-limited patient.