INTRODUCTION
Historically, direct laryngoscopy (DL) has been the primary method of performing tracheal intubation in the emergency department (ED). When utilizing DL, the goal is to compress and distract the tissues of the upper airway so that a direct line of sight can be achieved between the operator’s eye and the laryngeal inlet. Due to anatomic limitations, this can technically be very difficult and is simply not possible in some patients. Therefore, laryngoscopes were developed which could allow intubation to be completed by looking around the obstructing tissues rather than relying on their displacement. The introduction of fiber-optics into medicine helped to spur the development of rigid fiber-optic laryngoscopes such as the Bullard laryngoscope. These devices were essentially rigid laryngoscopes that incorporated a fiber-optic bundle and an eyepiece that allowed the operator to effectively see around the tongue. These fiber-optic laryngoscopes were clever in their design but required significant operator expertise to use them effectively. The inherent limitations of fiber-optics, such as their small field of view, requirement of an ocular eyepiece, lens fogging, and easy contamination, restricted their widespread use. When video cameras became miniaturized to the point where they could be placed onto a laryngoscope blade, new opportunities for laryngoscopy developed. Dr. John A. Pacey developed the first commercially available video laryngoscope (VL), the GlideScope, which has been in clinical use since 2001. The GlideScope incorporated a micro-video camera on the distal portion of the blade that connected to an external monitor via a cable. The video camera provided an indirect view of the airway and allowed intubation to be performed by using the video monitor. Since that time, numerous VLs have been developed and are in clinical practice. These devices differ considerably in their design. Some use conventional Macintosh curved blades, whereas others use hyperangulated blades. Some require freehand delivery of the tube by the operator, whereas others have a built-in channel guide for tube placement. Some have an external monitor connected to the laryngoscope by a cable, whereas others have a monitor attached directly to the laryngoscope handle. Some use disposable single-use blades, whereas others use reusable blades that can undergo high-level disinfection. What they all have in common is that they provide an indirect view of the laryngeal inlet, displaying the relevant anatomy on a video monitor allowing intubation to be performed without having to move any of the obstructing tissue out of the way. Additionally, the viewing angle is greatly increased over what is usually experienced with DL (10° vs. 60° with VL). Due to the many differences in design, a general overview of the use of VLs will be presented, followed by specific information for each device.
CLASSIFICATION OF VLs
The wide array of VLs can be fundamentally classified as standard geometry Macintosh blades and hyperangulated blades. Further, the hyperangulated blades can be further divided into those that have a tube guide and those that do not (see Table 14-1).
ADVANTAGES OF VL
VLs have many advantages over DL:
1. Obviate the need for direct line of sight to airway
2. Magnify the view of the airway
3. Require less force to intubate
4. Allow assistants to see and help with the procedure
5. Allow supervising practitioners to supervise procedure (even remotely)
6. Allow for recording of photos and videos which can be used for documentation and teaching
Classification of VLs |
Standard Geometry Macintosh Blade | Blade Sizes | Attached Screen | Reusable/Disposable | Pediatric Version |
C-MAC | Mac 2, 3, 4 Miller 0, 1 | Yes (requires special module) | R and D | Yes |
GVL Titanium MAC | MAC T3, T4 MAC S3, S4 | No | R D | |
GVL Direct | Mac 3.5 | No | R | No |
McGRATH MAC | Mac 2, 3, 4 | Yes | D | No |
Venner AP Advance | Mac 3, 4 | Yes | D | No |
Hyperangulated Blade | ||||
Channeled | ||||
King Vision | Adult | Yes | D | No |
Pentax AWS | Adult | Yes | D | No |
Venner AP Advance | Adult | Yes | D | No |
Vividtrac | Adult | No | D | No |
Unchanneled | ||||
GVL Titanium T3, T4 GVL Titanium S3, S4 | T3, T4 S3, S4 | No | R D | |
C-MAC D-blade | Adult | No | R | Yes |
McGRATH MAC X-blade | Adult | Yes | D | No |
CoPilot VL | Adult | No | D | No |
BASIC TECHNIQUE FOR VL
VL in general requires a different technique than DL. There are three important aspects to understanding VL. The following points apply generally to the technique of VL.
Visualization
With VLs, in contrast to DLs, the operator does not need to displace the tongue, but instead can look around it. Thus, there is no need to use the blade to sweep the tongue to the left as with DL. Instead the operator must use a midline approach. The VL should be inserted directly down the midline and advanced slowly while curling it around the base of the tongue. When introducing the blade it should be kept high and pressed against the tongue to avoid dipping the tip into the posterior oropharynx where it can get contaminated from pooled secretions. Once the epiglottis is identified, the tip of the blade should be advanced into the vallecula and a gentle lifting/rocking (primarily rocking) motion applied. The goal is to see the larynx in the top half of the screen. This leaves the bottom half of the screen available for visualizing the advancement of the endotracheal tube (ETT). A common mistake is to continue advancing the VL once an adequate view of the larynx is achieved. The problem that this creates is that it lifts the larynx higher and tilts it as well, making tube delivery much more difficult, and sometimes impossible.
Tube Delivery
Once an appropriate view of the larynx is achieved, the next goal is to direct the tube to the vocal cords. Since the tongue is not being displaced, the operator must direct the tube around the curve to reach what is being seen on the screen. An angulated stylet is needed for this. It is recommended to conform the styletted tube to match the curvature of the blade. Verathon makes a proprietary stylet called the GlideRite that is a rigid, curved stylet similar to the acute angle of the GlideScope blade. It is recommended that this stylet be used for any hyperangulated VLs. When it is time to introduce the tube into the patient’s mouth, the operator must take their attention away from the monitor and look at the patient. The tube is inserted into the patient’s mouth under direct observation. If the operator is still looking at the screen and not observing tube introduction directly, there is risk of damaging the structures of the upper airway such as the soft palate, tonsillar pillars, or posterior pharyngeal wall. After the tube is introduced under direct vision, the operator can then turn their attention back to the screen to see the tube as it enters from the right-hand side on the video monitor. At this point, the operator should begin to orient the tip of the tube so it points at the glottic opening. This should be done early and can be accomplished by rotating the tube to a vertical position and thereby making the angle at the end of the ETT point upward at the glottic inlet. The operator can continue to advance the tube to the laryngeal inlet by using the screen as a guide. The operator should attempt to pass the tube through the vocal cords as far as initially possible. Typically, some resistance will be encountered as the tip of the tube hits the anterior tracheal wall.
Tube Advancement
Once the tube passes the vocal cords and enters the trachea, the highly curved styletted tube will impinge on the anterior tracheal wall. At this point the stylet must be partially withdrawn by the operator or assistant so the tip of the tube will straighten out. The operator’s thumb can be used to withdraw the stylet a few centimeters back. The GlideRite stylet has a specially designed tab on it to facilitate this maneuver. It is important to recognize that the GlideRite stylet cannot be pulled straight out like a conventional malleable stylet. If this is attempted it will likely pull the tube out with it. The GlideRite stylet has an extreme curve and is very rigid and thus must be withdrawn from the tube in an arc over the patient’s chest to match its natural curvature.
COMPLICATIONS OF VL
When used properly, VLs are very safe and effective devices. Improper use, however, can result in untoward complications. For example, if the operator does not look at the patient while inserting the tube it is possible to traumatize the upper airway and even perforate some of these structures. When using a VL it can sometimes take longer to intubate because of difficulty directing the tube to what is being seen on the screen. This can be remedied by having the VL blade at the appropriate depth in the patient and using an appropriately shaped stylet.
GLIDESCOPE
The GlideScope was the first VL introduced into clinical practice and has undergone many modifications, with multiple units now available. The following is a description of the currently available units (Figs. 14.1A and B).
GlideScope AVL
The original GlideScope video laryngoscope (GVL) consists of a micro-video camera encased within a sharply angulated blade, a rechargeable video liquid crystal display (LCD) monitor, and a video cable that transmits the image. The monitor can be mounted on a mobile stand or attached to any available pole with a C-clamp. The laryngoscope portion of the GVL consists of a combined handle and laryngoscope blade that are made from durable medical-grade plastic. The video camera is placed in a recess midway along the undersurface of the laryngoscope blade, partially protecting it from contamination from bodily secretions. In addition, the GVL incorporates an antifog mechanism that heats the lens around the video camera, thereby decreasing condensation during laryngoscopy. There are four blade sizes for the GVL (GVL-2 through GVL-5). The GVL-2 is designed for small children (2 to 10 kg), whereas the GVL-5 is meant to overcome anatomic challenges seen with morbidly obese patients. The GVL size 3 and 4 blades are appropriate for small adults and large adults, respectively. Additionally, neonatal sizes are available with the single-use, Cobalt version. Because the GVL does not incorporate an ETT guide or stylet connected to the device, ETTs of any size can be used.
The laryngoscope attaches to a portable LCD monitor through a video cable that also carries power to light-emitting diodes (LEDs) mounted alongside the video camera. The monitor has a video-out port that requires a proprietary cable to connect to the composite video input, allowing the image to be transmitted to another monitor or recording device. The monitor can be rotated to the optimal viewing angle, and the cradle rests on a mobile telescoping pole that allows easy adjustment of the height of the monitor. The unit is powered by standard alternating current or its backup rechargeable lithium battery. The battery can provide 90 minutes of continuous use and has a low-battery indicator light to warn the operator that the unit must be plugged in.
GlideScope Ranger
The GlideScope Ranger is a rugged, portable, battery-operated GlideScope unit designed for field use. It is operational in a wide variety of temperatures, humidity, and altitudes and weighs roughly 2 lb (0.9 kg), making it very portable. It uses a 3.5-in (9 cm) LCD screen that allows good image clarity even when used outdoors. The Ranger can be used with a reusable blade or disposable Cobalt blades. The rechargeable lithium polymer battery provides 90 minutes of continuous use. The GlideScope Ranger is contained within a soft neoprene case for protection.
• FIGURE 14-1. GlideScope. A: The GlideScope Titanium series showing both the reusable hyperangulated T3 and T4 blades, and the reusable standard geometry Mac T3 and Mac T4 blades. B: The portable GlideScope Ranger.
GlideScope Cobalt
The GlideScope Cobalt is a disposable single-use version of the original GlideScope. The Cobalt consists of a flexible video baton that houses the micro-video camera that inserts into a disposable clear plastic protective blade, called the Stat. The Cobalt video baton may connect to either of two different video displays. The original Cobalt used the same color video LCD monitor as the GVL; however, this has largely been replaced by a newer version, the Cobalt Advanced Video Laryngoscope, which uses a high-definition video baton and digital video display. The monitor has similar dimensions to the original unit but has the benefit of a built-in tutorial as well as image and video clip acquisition that can be stored on a removable memory card. Currently, there are two baton sizes and five blade sizes available. The small baton works with Stat sizes 0, 1, and 2, and the large baton works with size 3 and 4 blades. The primary advantage of the Cobalt is its single-use design—eliminating logistic problems, costs, risks, and downtime associated with high-level disinfection of the traditional GlideScope.
GlideScope Direct Intubation Trainer
The GlideScope Direct Intubation Trainer, as its name implies, was developed to help teach practitioners DL. There is a single reusable metal blade available, size Mac 3.5. The operator can perform DL with this device while a supervisor uses the screen to help guide them.
GlideScope Titanium
The GlideScope Titanium is the newest product line introduced in the GlideScope series and consists of several different VLs. The GlideScope Titanium is a lightweight, low-profile
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