Video-Assisted Laryngoscopy and Its Effects on Difficult Airway Management

Abstract

Video-assisted laryngoscopy (VL) has become a critical tool in the anesthesiologist’s arsenal. Compared with direct laryngoscopy (DL), VL often improves laryngeal views, increases the frequency of first-attempt intubations, and decreases the time in achieving successful intubation. First-line utilization of VL has changed the approach to airway management, with some specialists indicating that VL will eventually replace traditional DL. In this chapter, we describe the history of video laryngoscopy, the advantages and disadvantages of currently available VL technologies, and its emerging utility in a variety of clinical settings.

1. Introduction

The techniques for managing a patient’s airway are constantly evolving. Historically, direct visualization of the vocal cords and related airway structures was required for each laryngoscopy. However, advances in technology have allowed for indirect laryngoscopy. Simply put, this technique involves visualizing the patient’s vocal cords without utilizing a direct line of site. Various forms of indirect laryngoscopy exist including fiberoptic bronchoscopes, fiberoptic stylets, mirror or prism optically enhanced laryngoscopes, and video laryngoscopes – the focus of this chapter. By using a laryngoscope equipped with a light source and video camera, a provider can visualize structures not within direct line of sight. The GlideScope®, developed in 1999 with the support of Dr. Jack Pacey, was the first video laryngoscope to be readily available. Since then, many different video laryngoscopes have been developed, each with its own advantages and disadvantages. In this chapter, we discuss the advantages and disadvantages of video laryngoscopy, differences in technique compared to direct laryngoscopy (DL), risks and benefits, various devices available, and what the current literature tells us about this airway technique compared to other utilized techniques.

2. Types of video laryngoscopes

As previously stated, the GlideScope® was the first readily available video laryngoscope. Today, many variations of video laryngoscopes exist, each with its own advantages and disadvantages when compared to one another. Video laryngoscopes can be broken down by two categories: blade type and whether they are channeled. Two main types of blades exist: the Macintosh blade and the acute-angle blade. Macintosh blades maintain the traditional shape as used in direct laryngoscopy. Acute-angle blades, as the name suggests, are hyper-angulated to allow for better anterior visualization. Channeled scopes are shaped to match the anatomic curve of the upper airway and the built-in channel provides a guided passage for the endotracheal tube. The different blade types and presence of a channel offer different advantages and disadvantages.

Examples of available Macintosh-style blades include the GlideScope®, Storz C-MAC (single and reusable), and McGRATH™ (single use). An advantage of these blades is most providers are familiar with this style of blade in terms of its shape and technique for use. The blade is shaped with the same angle as a direct laryngoscope. The provider follows the same initial steps for airway management including patient positioning, mouth opening, rightward insertion of blade, sweeping of the tongue, and direct advancement past the soft palate. At this point, the provider can continue use of this blade for direct visualization or indirectly visualize the airway using the device-specific video source. The blade is either directly or indirectly guided into the vallecula, and the epiglottis is lifted to expose the vocal cords. The provider directly visualizes the endotracheal tube entering the mouth and advancement past the soft palate after which the provider again has the choice of either directly or indirectly viewing the advancement of the tube through the vocal cords. It is important to stress the direct visualization of both the blade and tube past the oral cavity and soft palate as an indirect technique will put the patient at high risk for injury. The options provided by this type of blade allow for greater flexibility in technique for the provider and improved teaching of techniques, with all present having the ability to see what the laryngoscopist views. The video source allows for a supervising provider to see in real time what the performing provider sees, allowing for instruction or assistance on both direct and indirect techniques. For more difficult airways, the ability for multiple clinicians to view the airway can allow for earlier assistance.

As for acute-angle video laryngoscopes, examples of available devices include GlideScope® LoPro, Storz C-mac D-blade, and single-use GlideScope® AVL and McGRATH™ X-blades. These blades are oriented upward at a steeper angle as previously mentioned, allowing for better anterior visualization. For example, the GlideScope® blades are oriented upward at a 60-degree angle. Due to this angulation, these blades cannot be used for direct visualization and require the use of a stylet or tracheal introducer. The technique again begins with proper patient positioning and opening of the mouth in the same fashion as with direct laryngoscopy. The blade however is inserted midline and the tongue is not displaced. The blade is directly visualized until passing the soft palate. At this point, indirect visualizing of the blade into position is required. It is typically unnecessary to advance the blade fully into the vallecula, as deep insertion will rotate the laryngeal axis anteriorly, increasing the difficulty of endotracheal tube insertion. A shallower insertion will allow for a wider visual field, provide a straighter pathway for endotracheal tube delivery, and decrease both the distance from lips to the camera and the area of blind-zone during which the provider cannot see the tube tip. One study demonstrated a deliberately restricted view resulted in faster and easier tracheal intubation with no additional complications [1]. Gently lifting the blade will allow for proper visualization after which the endotracheal tube can be indirectly advanced past the soft palate and then indirectly passed through the vocal cords and removing the stylet prior to full advancement into the trachea.

Channeled blades are shaped to match the anatomic curve of the upper airway and to be positioned around the base of the tongue. This allows for exposure of laryngeal structures while reducing cervical manipulation and not requiring tongue displacement. The endotracheal tube is advanced through the channel and hence a limitation is that it is not possible to independently manipulate the tube. The bulkier design and limited use in patients with small mouth openings are additional disadvantages. Examples of these blades include AIRTRAQ AVANT, Airway Scope (Pentax), and King Vision (Ambu). Typically, these blades are entirely disposable or have single-use components.

3. Advantages and disadvantages of video laryngoscopy

Regardless of the specific blade or type of device utilized, video-assisted laryngoscopy (VL) increases the rate of successful intubation in elective airways, difficult airways, and those of the critically ill patient [2]. Certain devices allow for recording and capturing of images, which are useful again for teaching purposes or storing of various anatomical findings. The VL view can be saved in the patient’s record for future clinicians to observe and thereby provide critical clinical documentation that has historically been very much subject to the interpretation of the laryngoscopist. The VL, with its ability for multiple clinicians to simultaneously visualize the airway, has become a critical device for teaching and other settings where additional assistance may be necessary. Simple prior maneuvers, such as the BURP (backward, upward, and rightward pressure), become significantly more effective when the assistant is able to visualize the effects of the movement on the laryngoscopic view.

Because video-laryngoscopes are designed to allow for visualization of structures that are not within a direct line of sight, VL intubations are often of great benefit in patients with altered airway anatomy or suboptimal positioning, as the oral-pharyngeal-largyngeal axes do not need to be aligned for successful intubation. VL may reduce cervical spine motion and allow for lower lift force [3, 4]. It is postulated that VL reduces the stress response to laryngoscopy, though no current studies are available to show significant different hemodynamic differences between VL and DL techniques [5, 6, 7, 8].

There are still some opponents of VL technology, though there are fewer now than before due to the improvements in resolution, availability, and clinicians’ familiarity with these devices. Arguments against widespread VL use now focus on the cost and time to intubation. The setup of VL is certainly more expensive than DL, with components that may need sterile processing, increasing the yearly cost of airway management. While incidence of successful intubation has been documented, the time to successful intubation, with a maximum apneic limit of 60 seconds, has not been shown to be faster with VL over DL. Thus, the comparative advantage of VL over DL may not be superior. Additionally, the rise in VL use may significantly affect the art and practice of DL, which causes DL technique to suffer.

Videolaryngoscopy is not without potential complication. Reported incidence of videolarynscopy-related otolaryngologic complications is around 1%, with most injuries being minor [9]. Injury most likely with blind introduction of an endotracheal tube through the oropharynx, as the anesthetist is focused on the videolaryngoscope screen. Soft tissue injury may occur at various sites in the aerodigestive tract. While most injuries are minor lacerations, some palate injuries may require intervention by an otolaryngologist. Injuries that are recommended for immediate repair prior to extubation are gaping or perforated injuries with a hanging flap. It is important to evaluate and recognize such injuries in order to prevent potential negative consequences that may include bleeding, infection, retropharyngeal abscess formation, and potentially the inability to safely extubate the patient [10]. Proper training with appropriate visualization during intubation is essential to minimize such soft tissue complications.

4. Video laryngoscopy use guidelines

The 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway defines a difficult laryngoscopy as “not possible to visualize any portion of the vocal cords after multiple attempts at laryngoscopy”. Evidence cited in the guidelines support the use of video-assisted laryngoscopy in patients with predicted difficult airways. As stated in the guidelines, meta-analyses of randomized controlled trials comparing video-assisted laryngoscopy with direct laryngoscopy in these patients reported improved laryngeal views, higher frequency of successful intubations, higher frequency of first-attempt intubations, and fewer maneuvers with video-assisted laryngoscopy [4, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. Differences in time to intubation between the two techniques were equivocal [12, 14, 15, 16, 19, 20, 21, 22]. When comparing video-assisted laryngoscopy with airway laryngoscopy using a flexible intubation scope, randomized controlled trials reported equivocal findings for laryngeal view, visualization time, first-attempt intubation success, and time to intubation [23, 24, 25, 26]. In terms of which video laryngoscope is recommended, when comparing hyper-angulated video laryngoscopes with non-angulated video laryngoscopes for anticipated difficult airways, randomized controlled trials reported equivocal findings for laryngoscopic view, intubation success, first-attempt intubation success, and time to intubation [18, 20]. Additionally, comparisons of channel-guided with non-channel-guided video laryngoscopes found equivocal results for laryngeal view, intubation success, first-attempt intubation, time to intubation, and needed intubation maneuvers [17, 27]. VL is currently considered a first-line airway maneuver in airway management algorithms around the world and is being viewed as essential to standard of care in airway management.

5. Conclusions

As compared with direct laryngoscopy, video-assisted laryngoscopy often improves laryngeal views and increases the frequency of successful intubations. VL has become a very popular technique and is included in the Practice Guidelines of Difficult Airway Management for the American Society of Anesthesiologists, as well as other anesthesia societies world-wide. With the current widespread adoption of this technology, gaining familiarity with the various types of video-laryngoscopes that are now available is critical for any practitioner who is managing a patient’s airway.

Conflict of interest

The authors declare no conflict of interest.