Video Laryngoscopy
John C. Sakles
Calvin A. Brown III
Aaron E. Bair
INTRODUCTION
When the concept of orotracheal intubation was developed, more than 100 years ago, the procedure was performed blindly using palpation to identify the laryngeal inlet and guide the tube into the trachea. Shortly thereafter, laryngoscopes were invented, allowing for direct visualization of the larynx. These early laryngoscopes consisted of a metal spatula with a light bulb on the tip. The blade lifted the tongue out of the way, and the light bulb illuminated the glottic structures. The straight blade, or Miller blade, was introduced by Robert Miller in 1941, and 2 years later, Macintosh introduced the curved or Macintosh blade. Interestingly, little changed over the next five decades, and intubations largely were performed with Miller and Macintosh blades until the advent of video laryngoscopy from 2002 onward. This new approach to laryngoscopy involves placement of a micro-video camera along the laryngoscope blade to transmit glottic images to an external monitor, allowing the operator to perform tracheal intubation while watching the video screen instead of looking directly through the mouth. Video laryngoscopy has several important advantages over traditional direct laryngoscopy. First, fundamentally, video laryngoscopy transforms intubation from a technique requiring a straight line of sight from outside the patient’s mouth to the glottic aperture to one in which the image is acquired by the video camera, placed beyond the tongue, and requiring no such straight line of sight. Second, video laryngoscopy magnifies the view of the airway and allows the operator to see the airway in greater detail. Third, some video laryngoscopes have an exaggerated anterior angulation of the blade and this, along with the placement of the video camera, allows the operator to see structures that would be difficult or impossible to see under direct vision. Furthermore, video laryngoscopy can enhance education by allowing other health care providers to visualize the anatomy, and perhaps guide and offer assistance during the process of intubation. The use of a video laryngoscope also makes it possible to record the procedure to provide an excellent teaching resource and documentation for the medical record. There have been several video laryngoscopes introduced over the past few years. This chapter reviews the most important and well-studied video laryngoscopes currently available on the market.
DEVICES
GlideScope Video Laryngoscope
Device components
GlideScope system
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. There are three system configurations for the GVL system and two mounting options. The monitor can be mounted on a mobile stand or attached to any available pole with a C-clamp. An alternative configuration of the GVL is associated with a hard shell case with foam compartments housing the monitor, cable, and room for all three blades. This configuration may be ideal for mobile or remote field emergency applications.
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 eliminating fogging 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 endotracheal tube (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 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 Cobalt/Cobalt AVL
The GlideScope Cobalt is a disposable one-time use version of the original design. The Cobalt consists of a flexible video baton housing 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 uses the same color video LCD monitor as the GVL and is used in identical fashion as the original GlideScope. A new version, the Cobalt Advanced Video Laryngoscope (AVL), uses a high-definition video baton and digital video display (Fig. 13-1A). 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 four blade sizes available (GVL Stat sizes 1 to 4). The small baton works with Stat sizes 0, 1, and 2, and the large baton works with size 3 and 4 blades. The Cobalt blade is angled slightly more steeply than the original design. The primary advantage of the Cobalt is its single-use design—eliminating the logistical problems, costs, and downtime associated with high-level disinfection of the traditional GlideScope.
GlideScope Ranger
The GlideScope Ranger is a rugged, portable, battery-operated GlideScope unit designed for field use (Fig. 13-1B). 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 has two available blade sizes (Ranger GVL 3 and 4) both with a 60° viewing angle suitable for visualizing anterior airways. It also incorporates the antifogging system to maintain a clear view of the airway at all times. The video camera is positioned approximately halfway along the blade to protect the lens from contamination, including secretions, blood, and vomitus. The rechargeable lithium polymer battery provides 90 minutes of continuous use. The GlideScope Ranger is contained within a soft-sided case with belt attachments for ease of use and mobility. The manufacturer recently has developed the Ranger Single Use, which incorporates the Cobalt design within the Ranger system. Similar to the Cobalt, the Ranger Single Use has two different-sized batons and variably sized Stats.
Use of device
The GlideScope is intended as an everyday device for routine intubation and can also be considered an alternative airway device for difficult or failed airways. The device’s distal angulation makes it ideally suited to visualize and intubate an anterior larynx where direct laryngoscopy has proven unsuccessful. Because the handle has a narrow profile and does not require direct visualization of the larynx through the mouth, it is useful when cervical mobility or mouth opening is limited. Patients in whom it is desirable to minimize movement of the neck are excellent candidates because little force is needed to expose the glottis with the laryngoscope blade. The GlideScope generally performs well in the presence of secretions, blood, and vomitus, and thus is a good choice even in these circumstances.
The GlideScope is used in the following manner to perform tracheal intubation (Box 13-1 and Fig. 13-2). The handle is grasped with the left hand, in the same fashion as a conventional laryngoscope, and the tip of the laryngoscope blade is gently inserted into the mouth, in the midline, under direct vision. The critical point here is to keep the handle in the midline as you enter further into the mouth, noting key midline structures, such as the uvula, as you advance. There is no sweeping
of the tongue to the left as is done with conventional laryngoscopy. It is difficult to identify landmarks if the blade is off the midline. As soon as the tip of the laryngoscope blade passes the teeth, the operator should direct his or her attention to the video monitor and use the landmarks on the video screen to navigate to the glottic aperture. As mentioned above, the uvula will be seen if the blade is correctly situated in the midline. The operator should then continue to gently advance the blade down the tongue and past the uvula, with a slight elevating motion until the epiglottis is seen. At that point, it is best to continue advancing the blade into the vallecula, with some gentle upward force, to lift the epiglottis out of the way. The blade should ultimately be seated in the vallecula, much in the same way that a Macintosh blade is used. If the glottic view is insufficient, often a gentle tilt of the handle will expose it fully, in contrast to the lifting motion with a conventional laryngoscope. If the glottic aperture still cannot be exposed, the blade can be withdrawn slightly, placed under the epiglottis, and used like a Miller blade to physically displace the epiglottis up and out of the way. This motion can tilt the larynx more sharply, making advancement of the tube into the trachea technically more challenging. When an optimal glottic view (almost 100% of GVL views are either grade I or grade II) is obtained, the operator again looks into the mouth, to insert the ETT, with a stylet curved to match the curve of the GVL blade, alongside the blade. When the tube is placed where desired, the operator again views the video monitor to guide advancement of the tube to the glottis. Thus, intubation with the GlideScope can be thought of in four steps. For two of these steps, the operator is viewing the video monitor; for the other two, the operator is looking into the patient’s mouth (see Box 13-1).
of the tongue to the left as is done with conventional laryngoscopy. It is difficult to identify landmarks if the blade is off the midline. As soon as the tip of the laryngoscope blade passes the teeth, the operator should direct his or her attention to the video monitor and use the landmarks on the video screen to navigate to the glottic aperture. As mentioned above, the uvula will be seen if the blade is correctly situated in the midline. The operator should then continue to gently advance the blade down the tongue and past the uvula, with a slight elevating motion until the epiglottis is seen. At that point, it is best to continue advancing the blade into the vallecula, with some gentle upward force, to lift the epiglottis out of the way. The blade should ultimately be seated in the vallecula, much in the same way that a Macintosh blade is used. If the glottic view is insufficient, often a gentle tilt of the handle will expose it fully, in contrast to the lifting motion with a conventional laryngoscope. If the glottic aperture still cannot be exposed, the blade can be withdrawn slightly, placed under the epiglottis, and used like a Miller blade to physically displace the epiglottis up and out of the way. This motion can tilt the larynx more sharply, making advancement of the tube into the trachea technically more challenging. When an optimal glottic view (almost 100% of GVL views are either grade I or grade II) is obtained, the operator again looks into the mouth, to insert the ETT, with a stylet curved to match the curve of the GVL blade, alongside the blade. When the tube is placed where desired, the operator again views the video monitor to guide advancement of the tube to the glottis. Thus, intubation with the GlideScope can be thought of in four steps. For two of these steps, the operator is viewing the video monitor; for the other two, the operator is looking into the patient’s mouth (see Box 13-1).
 Figure 13-1 • A: The GlideScope AVL showing the video baton inside the transparent Cobalt Stat blade (right) and the newly introduced GlideScope Direct Intubation Trainer (left). The high-resolution digital screen is able to record still images, video clips, and has a built-in tutorial. (Photo courtesy of Kevin Reilly, MD.) B: The GlideScope Ranger. The cord wraps around the device, and the blade locks in place on the left-hand side. The blade and cord detach from the monitor and can be sent for sterilization. The “working light” on the handle is helpful when using the device in low-light conditions such as in the prehospital setting. (Photo courtesy of Kevin Reilly, MD.) |
Box 13-1 The Four-step Method for GlideScope Intubation
1. Look into the mouth to introduce the blade
2. Look at the monitor to obtain the best view of the glottis
3. Look into the mouth to introduce the tube
4. Look at the monitor to guide the tube through the glottis
 Figure 13-2 • Intubation Using the Standard GlideScope. Note that the operator has the GlideScope placed directly in the midline and is inserting the tube from the right side of the mouth. The inset photo demonstrates what the operator sees on the GlideScope monitor. Note that the larynx appears in the upper half of the view. This is by design so the operator can see and direct the “approach” of the tube to the airway. A small amount of blood is present on the interarytenoid notch and right vocal cord. |
Identifying and exposing the glottis generally is easy using the GlideScope. However, advancing the ETT toward the image of the glottis displayed on the video screen can still be challenging. Negotiating the oropharynx and traversing the glottis with an acutely shaped ETT can be somewhat technically difficult for two reasons. First, the GlideScope blade is angulated at 60°, and thus, the angle of attack of the tube is quite steep. The second issue is that using the screen to navigate to the glottis requires a form of hand-eye coordination that is different from traditional direct laryngoscopy. The critical factor in getting the tube to enter the trachea is configuring the ETT into a shape that conforms to that of the GlideScope blade so that the ETT is able to follow the same
trajectory as the blade. Under direct vision, the operator places the tip of the ETT in the corner of the right side of the patient’s mouth with the tube nearly parallel to the ground (operator’s hand at the 2- to 3-o’clock position) and advances the tube into position alongside the GVL blade. When the tube is felt to be well positioned, that is, proximate and parallel to the blade, the operator looks at the screen and advances the tube along its curved axis to guide it to the laryngeal inlet with the curvature heading anteriorly toward the airway. The manufacturer has developed a preformed rigid reusable ETT stylet (GlideRite Rigid Stylet) that is intended to provide an optimal curve and angle of approach to the glottis. If this stylet is not available, a malleable stylet can be shaped into a similar 60° curve. When the glottis is entered, the stylet is withdrawn 2 cm to reduce the rigidity of the sharply angulated distal tip of the tube, facilitating advancement into the trachea. Withdrawal of the stylet may be done by an assistant or by the intubator, particularly if using the proprietary stylet as it has a flange designed to be actuated by the operator’s thumb. The manufacturer of the GVL has recently released the GlideRite Auto Stylet, which has a mechanism to withdraw the stylet and advance the ETT with the simple push of a button on the stylet. If the tube continues to impinge on the anterior trachea, the GlideScope can be withdrawn about 2 cm, causing the larynx to drop down, lessening the angle of approach and thus greatly facilitating further advancement of the tube. Additionally, the ETT can sometimes become engaged on the arytenoids or the anterior tracheal wall because of the steep anterior angle through the glottis. Using a soft tapered tip ETT, such as the proprietary Parker ETT, can help overcome this issue and facilitate intubation by easing entry of the tube through the glottic inlet.
trajectory as the blade. Under direct vision, the operator places the tip of the ETT in the corner of the right side of the patient’s mouth with the tube nearly parallel to the ground (operator’s hand at the 2- to 3-o’clock position) and advances the tube into position alongside the GVL blade. When the tube is felt to be well positioned, that is, proximate and parallel to the blade, the operator looks at the screen and advances the tube along its curved axis to guide it to the laryngeal inlet with the curvature heading anteriorly toward the airway. The manufacturer has developed a preformed rigid reusable ETT stylet (GlideRite Rigid Stylet) that is intended to provide an optimal curve and angle of approach to the glottis. If this stylet is not available, a malleable stylet can be shaped into a similar 60° curve. When the glottis is entered, the stylet is withdrawn 2 cm to reduce the rigidity of the sharply angulated distal tip of the tube, facilitating advancement into the trachea. Withdrawal of the stylet may be done by an assistant or by the intubator, particularly if using the proprietary stylet as it has a flange designed to be actuated by the operator’s thumb. The manufacturer of the GVL has recently released the GlideRite Auto Stylet, which has a mechanism to withdraw the stylet and advance the ETT with the simple push of a button on the stylet. If the tube continues to impinge on the anterior trachea, the GlideScope can be withdrawn about 2 cm, causing the larynx to drop down, lessening the angle of approach and thus greatly facilitating further advancement of the tube. Additionally, the ETT can sometimes become engaged on the arytenoids or the anterior tracheal wall because of the steep anterior angle through the glottis. Using a soft tapered tip ETT, such as the proprietary Parker ETT, can help overcome this issue and facilitate intubation by easing entry of the tube through the glottic inlet.
The only absolute contraindication to use of the GlideScope is restricted mouth opening of <16 mm because this is the width of the widest portion of the blade.
The GlideScope GVL version laryngoscope blade/handle unit must be cleaned and disinfected after each use. Gross contaminants and large debris can be scrubbed off with a surgical scrub brush or enzymatically removed with a proteolytic compound such as Medzyme. Laryngoscope blades must undergo high-level disinfection. This can be accomplished with STERIS, STERRAD, ethylene oxide, or Cidex solutions, containing glutaraldehyde. The electrical connector cap should be placed over the contact port on the laryngoscope handle to prevent corrosion of the contacts. The only method of sterilization that is absolutely contraindicated is autoclaving, which involves exposure of the device to very high temperatures that will damage the electronic components of the video camera. In fact, the GlideScope has a silver temperature indicator on the side of the handle that turns black if the device is exposed to temperatures exceeding 80°C.
GlideScope Cobalt systems
Intubation is performed with the GlideScope Cobalt system in a manner analogous to that described above for the GVL. The major difference between this and the original version is the development of a disposable blade that attaches to a newly designed flexible video baton. The disposable blade slides easily over the flexible baton and locks in place with a notched mechanism. This combination provides a similar view to the original GlideScope, and the user can follow the previous recommendations for use. After the intubation is complete, the Stat can be removed, discarded, and returned to readiness by simply replacing the Stat. This design allows a more rapid turnaround time than sterilization. If necessary, the video baton can be cleaned and sterilized by using a nonautoclavable method such as STERRAD or STERIS.
GlideScope Direct Intubation Trainer
The GlideScope Direct Intubation Trainer (GVL Direct) is the newest addition to the GlideScope family of video laryngoscopes. Although clinical use of video laryngoscopy has been growing rapidly, health care providers continue to learn and maintain skills in direct laryngoscopy. To that end, the GVL Direct was developed (Fig. 13-1A). The GVL Direct is a metal blade that has the same look and feel of a standard Macintosh blade (roughly equivalent to a Macintosh “3.5”), except that it has a video camera on the undersurface of the blade. This allows the operator to perform a conventional direct laryngoscopy while an instructor monitors the procedure on the GlideScope monitor. Alternatively, if the operator has difficulty visualizing the airway during direct laryngoscopy, the video monitor can be used to facilitate visualization and complete the intubation
videoscopically. The GVL Direct can be used in the same fashion as the other GVL blades or in a manner used for direct laryngoscopy. If intended for use as a video laryngoscope, the blade is inserted down the midline, and when used as a direct laryngoscope, it should be inserted in the right-hand corner of the mouth so that the tongue can be swept to the left, as for direct laryngoscopy (see Chapter 12). At the time of this writing, there have been no studies using the GVL Direct, but preliminary clinical experience demonstrates a very high rate of success with this device for emergency intubations. The GVL Direct thus shows promise both for use as a direct laryngoscope (particularly in a training setting) and as a video laryngoscope, either primarily or when intubation through direct visualization is not possible.
videoscopically. The GVL Direct can be used in the same fashion as the other GVL blades or in a manner used for direct laryngoscopy. If intended for use as a video laryngoscope, the blade is inserted down the midline, and when used as a direct laryngoscope, it should be inserted in the right-hand corner of the mouth so that the tongue can be swept to the left, as for direct laryngoscopy (see Chapter 12). At the time of this writing, there have been no studies using the GVL Direct, but preliminary clinical experience demonstrates a very high rate of success with this device for emergency intubations. The GVL Direct thus shows promise both for use as a direct laryngoscope (particularly in a training setting) and as a video laryngoscope, either primarily or when intubation through direct visualization is not possible.
At the time of this writing, the manufacturer of the GlideScope announced some new GlideScope products that are on the near horizon. One version of the GVL will have a tube guide on the anterior surface of the blade to direct the tube through the glottis inlet without the need for a stylet. The channel blade will be available in a reusable version, as well as a disposable stat blade that covers the handle as well as the blade to mimimize infection transmission. The GlideScope Direct trainer system is to be expanded to include a disposable blade. A new pediatric Cobalt blade, size 2.5, will allow for intubation of children up to 5 years of age. A novel apneic oxygenation stylet will deliver oxygen at up to 15 L per minute. This has the potential to reduce periods of hypoxia during the intubation.
Summary
The GlideScope is a rugged, well-designed device designed for both routine and difficult intubation. There are multiple configurations and blade sizes that allow the devices to be used in a variety of clinical situations. Because of its anterior video angulation, antifog capabilities, and capacity to maintain an adequate view despite secretions, the GlideScope is particularly useful for anticipated or identified difficult emergency intubations.
C-MAC Video Laryngoscope
Device components
The C-MAC video laryngoscope system (Karl Storz, Tuttlingen, Germany) replaces earlier versions of hybrid video-fiberoptic systems. The C-MAC system uses a CMOS micro-video camera, which provides an enhanced field of view and resists fogging. The device also incorporates a video recording system, with controls on the handle, which supports both teaching and quality management. The C-MAC is powered by a rechargeable lithium battery, permitting 90 minutes of operation without a power source. The system comprises a variety of blades that accommodate the video camera, which connects through a single cable to a 7-in (17.8 cm) video screen, with straightforward controls (Fig. 13-3
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