Abstract
Videolaryngoscopes have been in existence for several decades but in the last decade have taken a central role in both difficult and routine airway management. During that time videolaryngoscopy has not only become embedded in most difficult airway algorithms but the technique has become part of core airway management skills and the use of awake videolaryngoscopy has increased. This chapter describes the various types of videolaryngoscopes, their roles, strengths and limitations. Strategies to optimise use of Macintosh and hyperangulated devices are described as well as which adjuncts are best suited to their use. The issue of ‘can see, cannot intubate’ is discussed along with techniques to overcome it. The role of videolaryngoscopy outside the operating theatre, in critical care, in the emergency department and in pre-hospital care is discussed in this and other chapters.
Introduction
Videolaryngoscopy has all but evolved to a gold standard for difficult laryngoscopy and intubation. A multitude of videolaryngoscope (VL) devices and designs are available. Videolaryngoscopes can be categorised into three main types according to their blade type:
Macintosh-like blade
hyperangulated blade
blade with an integrated tracheal tube-guiding channel (i.e. a conduit)
Each of the three designs have their indications and each requires distinctive training and specialised handling. Related to VLs are video stylets, which are also briefly described in this chapter.
Videolaryngoscopy provides technical benefits and significant non-technical benefits to the intubation team. Consistently, VLs improve laryngeal view compared with direct laryngoscopy. The ability of other team members (or trainers) to observe what the primary intubator is seeing when using a VL fosters enhanced teamwork and learning.
Development
Traditionally, laryngeal structures can be visualised either indirectly, e.g. by using mirrors, or directly, by the use of standard laryngoscopes. For the last 20 years, with the recently expanding variety of VLs available, the anaesthesia community has gradually turned to indirect laryngoscopy as the favourite means to visualise the larynx. The impact of videolaryngoscopy on tracheal intubation is easily comparable to the introduction of Macintosh’s laryngoscope blade in 1943. It may not be as revolutionary as the introduction of the supraglottic airway device, but it is arguably the most important advance in airway management in recent decades.
The concept of introducing not only light to the tracheal opening, but also a camera, was introduced to the anaesthesia community quite some time ago. A variety of flexible optical bronchoscopes (FOBs) (see Chapter 16) were in use since the 1970s and rigid optical scopes followed afterwards. One rigid optical scope, combined with a laryngoscope, is the Bullard laryngoscope (Figure 17.1). It features important characteristics of modern VLs with a hyperangulated blade: it provides an optical scope, albeit with the eye at the tip of the tracheal tube and not at the tip of the blade, and a very angulated blade to facilitate intubation around anatomical obstacles at the base of the tongue. As such, it did not require the alignment of the glottis on the same axis with the line of sight, which is a prerequisite for direct visualisation of the laryngeal structures.
At the beginning of the twenty-first century, the concept of placing a camera on the laryngoscope blade started to be marketed. First, on a standard Macintosh blade equipped with a fibreoptic scope (e.g. Laryflex by Acutronic, Hirzel, Switzerland, Figure 17.2, and Storz DCI Videolaryngoscope, Karl Storz, Tuttlingen, Germany). The cumbersome assembly and cleaning prohibited widespread use. Dr John Allen Pacey, a surgeon, introduced a sharply angulated blade with a digital camera in 2001, the GlideScope (Verathon, Inc., Bothell, WA, USA, Figure 17.3). This device featured a CMOS (complementary metal-oxide semiconductor) digital chip and LED (light emitting diode) light to enable portability and reduced assembly needs. Since then, a wide range of VLs have become available, with different features and designs.
Figure 17.3 The GlideScope Go.
Studies comparing the success rate of tracheal intubation between standard laryngoscopy and videolaryngoscopy are often insufficient because of inconsistent methodology. Hyperangulated blades are very different from Macintosh blades and also very different from blades with an integrated tube-guiding channel (conduit). Regardless of study limitations, there is ample evidence available to confirm VLs are superior to standard laryngoscopes in providing an improved laryngeal view.
Compared to standard laryngoscopy, tracheal tube advancement may be more difficult, especially with hyperangulated blades. This is most commonly due to the operator having inadequate knowledge or experience of videolaryngoscopy technique. Inadequate training or experience should not be confused with a limitation of the technique and it is important to understand that there is a learning curve for all VLs, but particularly for hyperangulated and conduited devices. When correctly performed, the use of videolaryngoscopy is associated with higher intubation first-attempt success rates, fewer oesophageal intubations and less sore throat and hoarseness.
An often-overlooked aspect of the use of VLs is one of the most important ones: using a screen to view the intubation procedure provides the opportunity to evolve the intubation procedure from a manoeuvre performed solely by one laryngoscopist to a task performed and guided by a team. The team approach may optimise intubation attempts (e.g. an assistant providing optimal external laryngeal pressure or adjusting cricoid force) and can help prevent errors such as oesophageal intubations, as helpful hands and eyes can support the intubation procedure. It is also possible to record the intubation process for teaching purposes and legal documentation. The record can now serve to document the ease or difficulty of the procedure and to confirm proper tube placement without signs of injury or aspiration.
Overview of Different Videolaryngoscopes
When choosing a VL, the type of blade is the most important decision (Figure 17.4). Several manufacturers offer both hyperangulated and Macintosh blades. Blades with conduits are routinely hyperangulated.
Furthermore, both single-use and reusable systems are available. While the performance is similar, differences regarding financial, logistic, environmental and hygienic issues guide purchase decisions.
Use of Videolaryngoscopes with a Macintosh-Type Blade
Videolaryngoscopy with a Macintosh-type blade closely resembles direct laryngoscopy. For practitioners experienced with standard laryngoscopy who are new to using VLs, it may be prudent to start with a Macintosh-type VL blade. The transition is much smoother and the early failure rate may be lower. Another advantage is the opportunity to readily switch back to direct laryngoscopy, e.g. in case of severe contamination of the lens or the presence of ambient light, especially in pre-hospital environments.
A ‘patient–screen–patient’ approach is recommended, just as in regional anaesthesia with ultrasound. Thus, the operator looks at the patient when advancing or moving the blade and then at the screen to observe the effect of that movement – while holding the device still. Again, when inserting the tracheal tube, the operator does not look at the screen until the tube is advanced beyond the line of sight at the posterior pharynx. The advancing of the tube towards and beyond the glottic opening may be observed either directly as in standard laryngoscopy, or by observing the screen.
Intubation may be facilitated by using either a tracheal tube with a stylet inserted or an intubation aid (a ‘bougie’) (see Chapter 15).
Use of Videolaryngoscopes with a Hyperangulated Blade
The advantage of using a hyperangulated blade lies in the ability to look around obstacles at the oropharyngeal curve, such as a prominent base of the tongue, which would impede or defeat direct laryngoscopy. Hyperangulated blades may be inserted along the side of the tongue (like a Macintosh-type blade) or in the midline. In either case the tip of the blade should be placed in the vallecula. Minimal force should be needed to place the blade and this is one of its advantages.
In most circumstances a hyperangulated blade will improve the view of the larynx, compared with direct laryngoscopy. However, intubation may not necessarily become easier – though this is most commonly due to poor operator technique. When passing the tracheal tube, it must pass through the two curves of the upper airway: first anteriorly to meet the glottic inlet, then posteriorly to lie along the tracheal axis. This problem has been termed as ‘you see that you fail’: the tracheal tube is not passed despite a perfect view of the glottis. Successful intubation with a hyperangulated VL mandates a stylet (or another semi-rigid introducer) with an angulation resembling the angle of the blade. The manufacturers of the GlideScope and C-MAC devices each market their own rigid stylet with this preformed configuration. Once a tracheal tube has a stylet within it, it becomes more rigid and if care is not taken, the tube or stylet may injure the posterior wall of the pharynx (Figure 17.5). This complication is closely associated with hyperangulated blades and evidence supports an expected 1% event rate. The hyperangulated blade means it is inevitable that the tip of the tracheal tube will pass out of direct sight during insertion. It may not then appear on the VL screen until it is advanced a little further, meaning there is a ‘blind spot’ when the tube tip is visible neither directly nor indirectly. In practice this blind spot is very small. Also, if the tip of the tracheal tube is slid along the blade as it disappears from view this should minimise contact with the posterior pharyngeal wall and virtually eliminate the risk of injury.
