Extraglottic Devices: Retroglottic Type

INTRODUCTION

The term extraglottic device (EGD) is divided into two main subclasses: supraglottic devices and retroglottic devices. Supraglottic devices are defined and discussed in Chapter 10, along with general indications and contraindications. This chapter focuses on the retroglottic EGDs (rEGD). Since these devices sit posterior to the glottis in the proximal esophagus, they are contraindicated in patients with known esophageal disease such as strictures and presumed esophageal disease as in caustic ingestions; otherwise, they share the same indications and contraindications as the supraglottic EGDs.

Retroglottic devices such as the Esophageal Obturator Airway and the Esophageal Gastric Tube Airway were among the first extraglottic airways to be put into practice, back in the 1970s, but no longer have a role in emergency airway management. Modern rEGDs represent a dramatic improvement over these early devices and have demonstrated their effectiveness and safety in rapidly establishing oxygenation and ventilation in a variety of emergency situations.

RETROGLOTTIC DEVICES

To many practitioners, the most familiar and prototypical EGD is the Esophageal-Tracheal Combitube (ETC) (Fig. 11-1) (Tyco-Healthcare-Kendall-Sheridan, Mansfield, MA). It has been in use since 1987 and has substantial evidence and experience supporting its use. It is generally easier to use and more effective for novices than is BMV and easier to place than an endotracheal tube (ETT). The success of the ETC has spawned the development of devices based on the same principles, attempting to replicate or improve on its safety, ease of use, and ability to facilitate oxygenation and ventilation. These most common of these devices, and the two examples discussed in this chapter, include the Rusch EasyTube (Fig. 11-2) and the King Laryngeal Tube (King LT) (Ambu Inc. USA Columbia, MD) variants (Fig. 11-3).

All of these devices share the design feature of two high-volume, low-pressure balloons. The proximal balloon seals the oropharynx, whereas the distal balloon seals the esophagus, with gas exiting and entering the device and the laryngeal inlet between the two. The ETC and the EasyTube use two separate inflation ports to enable independent balloon inflation; the King LT has a single inflation port that inflates both the upper and lower portions of the balloon with a single bolus of air. The advantage of the latter is simplicity, but during tube device exchange it is beneficial to be able to maintain esophageal occlusion while deflating the upper balloon for laryngoscopy. The ETC and EasyTube both have dual lumens that allow for ventilation whether the device ends up in the proximal esophagus as intended or in the trachea; the King LT has a single lumen based on the reality that placement of these devices almost always results in esophageal positioning.

• FIGURE 11-1. The Combitube Inserted and Seated. Note how the laryngeal aperture is trapped between the two balloons.

• FIGURE 11-2. Rusch EasyTube.

In common practice these devices are all inserted blindly, but there is a strong literature base supporting direct visualization for placement of the ETC when the equipment and expertise exists, which can be extrapolated to the EasyTube and possibly even the King LT. Such placement technique may mitigate some of the common issues encountered with these devices during insertion, particularly trauma to the posterior pharynx.

• FIGURE 11-3. The King LT Airway. Note that there is only one inflation port to inflate both balloons.

When compared with SGDs, retroglottic EGDs typically have a tighter seal, resulting in higher cuff leak pressures (up to 35 to 40 cm H₂O compared with 25 to 30 cm H₂O), which may be advantageous in patients with intrinsic high airway resistance requiring high peak airway pressures (asthma and obesity) or if glottic anatomy is distorted from hematoma, infection, or mass, requiring increased inflation pressure. These devices may also provide some tamponade effect for upper airway bleeding. There is some concern that these devices exert more pressure on the carotid vessels than do SGDs. This might increase vagal tone and impede resuscitation efforts, leading some to advocate for SGDs over rEGDs as the airway device of choice during cardiac arrest. This concern arose largely from animal (swine) study and has been countered in a small human case series.

Combitube

The ETC (Fig. 11-1) has been in clinical use for a much longer period of time than any of the other EGDs and therefore it has accumulated the largest body of evidence describing its indications, contraindications, benefits, and risks. As discussed above, the ETC is a dual-lumen, dual-cuff, disposable rEGD intended to be inserted into the esophagus, although it may rarely enter the trachea on insertion (generally <5% of insertions) and is designed to function adequately in either position. The ETC is supplied in two sizes: 37F catheter SA (small adult) and 41F catheter Regular, which, according to the package insert, are to be used for patients 4 ft (1.22 m) to 5 ft 6 in (1.67 m) tall and more than 5 ft 6 in tall, respectively. However, postmarketing research has demonstrated that the small adult size should be used all the way up to 6 ft tall. There is no ETC suitable for use in children or patients <4 ft tall. Due to its large robust balloons, the ETC can generate some of the highest peak ventilation pressures before leak occurs (up to 40 cm H₂O) and may be the EGD of choice when ventilation is predicted to be challenging.

The Combitube has been shown to be an easy and effective primary airway, particularly in the prehospital setting, and rescue airway in the event of a failed intubation. Like any EGD, it does not provide optimum protection against aspiration, although the protection provided is substantial and reports of aspiration are infrequent. The relative merit of the ETC compared with all the available newer retroglottic and supraglottic devices is not well established.

Insertion Technique

Insertion of the Combitube is typically a blind technique intended for providers that do not have training in laryngoscopy; however, a laryngoscope can and should be used when available to lift the tongue and permit direct visualization of esophageal placement, as was done in all the preliminary trials in the operative setting. Although the Combitube has been inserted in almost every conceivable patient position, the technique described here assumes the patient is in the supine position and the provider does not have a laryngoscope available or cannot perform laryngoscopy within their scope of practice.

• FIGURE 11-4. Lipp maneuver.

1. First perform a Lipp maneuver to gently preshape the device to pass easily around the tongue (Fig. 11-4).

2. With the patient supine and the head and neck in a neutral position, lift the tongue and jaw upward (jaw lift) with the nondominant hand.

3. Insert the preshaped device in the midline, allowing the curve of the device to follow the natural curve of the airway around the tongue, and advance the device until the upper incisors (or alveolar ridge if the patient is edentulous) lie between the imprinted black circular bands on the device. Minimal force is required to enable the device to pass through the pharyngeal constrictor muscles into the esophagus; resistance should prompt the operator to withdraw, reassess patient positioning and device shape, consider use of a laryngoscope, and gently readvance. Using the syringe provided, inflate the proximal large oropharyngeal balloon with 100 mL of air (Regular) or 85 mL of air (SA) through the blue pilot balloon port labeled no. 1.

4. Inflate the distal small balloon with 15 mL of air (Regular) or 12 mL of air (SA) through the white pilot balloon port labeled no. 2. This presumes the device is sitting in the distensible upper esophageal tissues.

5. Begin ventilation using the longer blue connecting tube (labeled no. 1), which will deliver air out the ventilation holes on the side of the device between the proximal and distal balloons. The presence of air entry into the lung, the detection of end-tidal carbon dioxide, and the absence of gastric insufflation by auscultation all indicate that the Combitube is situated in the esophagus, which occurs with nearly every insertion. With the Combitube in this position, aspiration and continuous suctioning of gastric contents is possible by passing the provided suction catheter or any 12F catheter or smaller catheter through the clear connecting tube (labeled no. 2) into the stomach.

6. If ventilation using the longer blue tube no. 1 does not result in breath sounds and end-tidal carbon dioxide detection, then the Combitube may have ended up in the trachea and ventilation should be attempted through the shorter clear connection tube no. 2. In this case, air should be withdrawn carefully from the distal balloon until an air leak is just heard and then just enough added back to overcome the leak to avoid pressure injury in the trachea. In this tracheal position, gastric decompression through the device is not possible.

7. The absence of end-tidal CO₂ and any sounds on auscultation while ventilating both ports may indicate severe patient pathology, incorrect sizing, or that the device has been inserted too far and should be withdrawn carefully.

Complications

Complications are rare, but occasionally very serious and likely underreported, with most related to upper airway and esophageal trauma from overly aggressive insertion or balloon overinflation. These include hematomas, mucosal lacerations, pyriform sinus perforation, and perforation of the esophagus. Most complications can be overcome with proper training and technique. Other issues are related to potential mucosal ischemic injury and possible impairment of carotid blood flow as discussed above. Finally, it should be noted that the pharyngeal balloon on the Combitube (as opposed to the Rusch EasyTube or the King LT airway) is made of latex and should be avoided in patients with this allergy.

Rusch EasyTube

The Rusch EasyTube (Fig. 11-2) is a dual-lumen tube designed for difficult or emergency airway intubation and ventilation. Like the Combitube, the EasyTube can be placed either in the trachea or in the esophagus and creates a viable airway in either position. When placed in the esophagus, the EasyTube allows the passage of a flexible endoscope, a suction catheter, or a tracheal tube introducer through the proximally terminating ventilation lumen. This distinguishes it from the Combitube, which does not permit passage of a tube exchanger to potentially establish a definitive airway through the device. If placed in the trachea, the size and shape of the distal tip are similar to a standard ETT. It is suggested by the manufacturer that the risk of tracheal trauma relative to the Combitube is reduced because of the smaller diameter of EasyTube device at the distal tip.

The EasyTube is latex free and supplied in two sizes, 28F catheter and 41F catheter. As for the Combitube, the manufacturer claims that the smaller size can be used in older children. There is minimal evidence from human studies to demonstrate the relative success rate of the EasyTube versus the LMA, Combitube, or King LT, although initial data appear promising. Multiple manikin studies show that it is similar to a Combitube in speed of insertion, successful ventilations, and skill retention. More data are needed to determine its role in emergency airway management.

The Laryngeal Tube Airway

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