Unanticipated Difficulty

Every patient in any environment has the potential for unexpectedly being difficult to intubate. Unexpectedly encountering blood, emesis, a mass, an anatomic variant, or evolving traumatic injury can all result in a challenging airway. In this chapter we attempt to organize and briefly define some of the many rescue techniques that might be used in emergency practice.

Anticipated Difficult Airway

Only a small fraction of patients undergoing ED intubation are actually deemed poor candidates for RSI, even though many patients are expected to be difficult to intubate. No discreet threshold at which RSI is deemed to be safe and when it is contraindicated has ever been determined, partly because of the lack of sensitivity of the various difficult airway prediction tools. Importantly, many ED patients are in extremis and unable to cooperate with a preprocedural examination.^21,²² Much of what is discussed in the current literature is based on the anesthesia experience, which generally reflects the “elective” intubation of cooperative patients. Nevertheless, it is often useful to perform a preprocedural assessment, as allowed by time constraints and the patient’s condition. Some evaluation is necessary to be able to accurately estimate the potential for encountering a difficult airway.

The algorithm presented in Figure 2.1 represents a clinical approach to a difficult airway.⁷ Application of such an approach is predicated on the answers to several key questions:

• Is there enough time to plan a methodic approach?

• Despite the identified presence of difficult airway predictors, can RSI still be used safely?

• Is the patient’s oxygenation adequate?

Fig. 2.1 Difficult airway algorithm.

ETT, Endotracheal tube.

(Adapted from Walls BM. The emergency airway algorithms. In: Walls RM, Murphy MF, editors. Manual of emergency airway management. 3rd ed. Philadelphia: Lippincott Williams & Wilkins; 2008.)

Understanding these issues in context to a given clinical scenario will help in the decision-making process regarding alternative approaches.

Rapid-Sequence Intubation for A Difficult Airway

RSI is preferred for the vast majority of intubations performed in the ED. It is important to realize that provider familiarity will probably be the major determinant regarding device and technique selection beyond the use of RSI. For this reason it is prudent to focus on techniques that are likely to remain familiar through frequent use. Accordingly, the use of optimized and augmented laryngoscopy merits discussion because these concepts are simply extensions of “routine” RSI.

Optimized Laryngoscopy

Routine direct laryngoscopy relies on manipulation of the soft tissues of the hypopharynx and the base of the tongue into the relatively fixed proportions of the mandible. The goal of such manipulation is to allow a direct line of sight to the larynx and vocal cords. This, however, can be difficult given certain unalterable variables of patient anatomy. The process of optimizing the view is probably the simplest and often the least appreciated of the skills of an expert airway manager. The features of optimization are discussed in the following sections.

Augmented Laryngoscopy

This concept refers to using an assistive device to either extend the view of the intubator (i.e., fiberoptic stylet) or assist in tube placement with use of a narrow-diameter introducer. Such introducers have been used for decades and come in various formats (i.e., Eschmann, Frova). The leading tip of these introducers is angled anteriorly to provide tactile feedback regarding location of the introducer. These devices can be valuable when visualization is limited.

Alternative Techniques for the Anticipated Difficult Airway

Fiberoptics

As a class, directable and flexible scopes have been available for decades. They have recently been made more portable by replacing the heavy light source with a battery pack. These devices are consequently more convenient in the harried ED. The majority of the products currently on the market consist of a directable cable mechanism associated with a light source and fiberoptic bundle. Notable issues are that the glass fibers that constitute the optics are breakable and small amounts of debris can greatly diminish viewing quality. Historically, these devices were considered too expensive or impractical. In the future, however, these type of flexible and directable devices will probably become more available. To date, relatively little research relevant to emergency medicine practice has been conducted.^2,²⁷^–²⁹ A recent query of emergency medicine training programs in the United States suggests that the majority maintain this type of equipment,¹¹ but clinical expertise is variable.

Flexible and Directable Fiberoptics

Flexible and directable fiberoptic models are portable and have variable diameters and lengths. This equipment varies depending on its intended purpose. The shorter nasopharyngoscope is approximately 35 cm in length, in contrast to the 60-cm bronchoscope. The goal is to directly visualize the glottis via the nares or mouth. Once the cords are visualized, the tip of the fiberoptic scope is advanced into the airway to the level of the carina. The preloaded endotracheal tube is then advanced over the scope and into the airway. Efficacy of this technique in an awake patient requires adequate patient and equipment preparation (Box 2.2).

Box 2.2 Patient Preparation

If using a nasal approach, adequate topical anesthesia and vasoconstriction can be achieved with various agents via an atomizer.

If using an oral approach, various spray anesthetic agents can be used in addition to a nebulized agents (e.g., lidocaine). Additionally, gargled lidocaine (4%) can be effective, patient cooperation permitting.

An antisialagogue (e.g., glycopyrrolate) can be useful to allow better tissue absorption of topical anesthetic agents. However, at least 20 minutes is needed for efficacy as a drying agent.

Sedation is used, as necessary, to achieve reasonable anxiolysis to improve patient cooperation.

Preoxygenation, as always, is fundamental to procedural sedation and airway management.

Tips and Tricks

Even though a complete tutorial of the technical details of using flexible fiberoptics is beyond the scope of this review, several technique pearls are worth highlighting:

1. Recognize that the procedure will take at least 15 to 20 minutes to accomplish. If the patient cannot tolerate such a wait, use of this technique may be misguided.

2. Stay in the anatomic midline at all times during the procedure. Straying laterally will often result in poor visualization and inability to pass the vocal cords.

3. Keep the slack out of the scope. If slack is present along the length of the scope, rotation of the body of the scope will not translate into rotation of the tip.

4. The size of the working channel in many scopes is often too small for suction to be effective.

5. If the tube is resistant to passage of the scope into the airway, it is likely that the tip of the tube, or Murphy’s eye, is caught at the level of the arytenoids. Rotation of the entire tube-scope apparatus 45 to 90 degrees will probably overcome the obstruction.

6. Further considerations:

• Nasal approach. This route may be better tolerated by the patient and will not subject the equipment to damage from biting by the patient. However, it is prone to cause bleeding with passage of the tube. Adequate vasoconstriction is key. Partially intubating the chosen naris with the endotracheal tube can often simplify the procedure by avoiding the obscuring materials in the nasopharynx. Beware, however, that placing the tip of the tube too deep into the posterior pharynx will make subsequent scope manipulation challenging because of the acute angle that will be required for the tip of the scope to reach the glottis. Optimally, the tip of the endotracheal tube should be placed at the level of the uvula before attempting to advance the scope to the vocal cords.

• Oral approach. This may be advantageous if a larger endotracheal tube is needed. However, a bite block or a device that provides an oropharyngeal conduit may be necessary if there is a possibility of the patient biting the equipment. Additionally, a fiberoptic technique can be used in conjunction with a second provider using a laryngoscope to manipulate the soft tissues of the oropharynx.

• Adjunctive use. Use of flexible fiberoptics through a laryngeal mask airway or similar device has been described.³⁰^–³³

Flexible and Nondirectable Fiberoptics

Flexible and nondirectable fiberoptics have been designed to be used from within the lumen of an endotracheal tube. They all share in common the issues related to obscuration of view with debris. Additionally, any attempt to direct the tip of the device relies on manipulation of the associated endotracheal tube with visual feedback through either an eyepiece or video monitor. Despite these shortcomings, these devices are attractive because the nondirectable group is generally regarded as more durable and tends to be less expensive. An example of this type of device is the Trach View (Parker Medical, Englewood, CO).

The semirigid fiberoptic scope is, conceptually, a semimalleable stylet with internal fiberoptic bundles.³⁴ These devices are similar to the nondirectable class of fiberoptics with respect to image quality and durability. An example of this type of device is the Shikani optical stylet (Clarus Medical, LLC, Minneapolis, MN).