Other Supraglottic Airway Devices

Kristin Schreiber

Paul Bigeleisen

Concept

There are several indications for the use of a supraglottic airway device (SGA), particularly when the patient cannot be intubated or ventilated using bag-mask ventilation. In this case, successful placement of an SGA defines an emergent versus a nonemergent pathway. Although the laryngeal mask airway (LMA) and Combitube have traditionally been used in this context, the devices discussed in this chapter can also serve this purpose. Other important uses include airway management by practitioners with variable experience using direct or optically guided intubation. In the operating room, SGAs can be used in elective, spontaneous ventilation cases. In addition, some of these devices allow multiple simultaneous functions (ventilation, intubation, and gastric decompression).

One of the most important qualities when selecting an SGA is its ease of use, as it is often used in an emergent situation. Improper placement of the various SGAs is also an important consideration, as obstruction or air leak can result in difficult ventilation, ultimately increasing the risk of gastric distension and aspiration. Although supraglottic airways have a design that seeks to protect the lungs from aspiration of gastric contents or of pharyngeal secretions/blood, an endotracheal tube (ETT) has generally been considered to provide superior protection from aspiration. The results of some studies, however, suggest that aspiration occurs in 11% of cases even when ETTs are used properly.¹ In a comparison study of aspiration, episodes of hypopharyngeal pH <4 were similar in incidence between a COBRA, LMA, laryngeal tube (LT), and ETT, suggesting that the ETT may not provide superior protection against aspiration.² Finally, the cost and disposability of the device impacts the ability of trainees to practice and become proficient with the device.

Categorization of Supraglottic Airways

One proposed categorization scheme for supraglottic airways is based on the mechanism of sealing around the glottic aperture.³

1. The perilaryngeal cuffed group includes the LMA and all of its variants (reviewed in Chapter 26).
2. The pharyngeal and esophageal cuffed devices include the Combitube and LT (King).
3. The pharyngeal cuff only includes the COBRA.
4. The cuffless anatomically shaped sealers include devices such as the Streamlined Liner of the Pharyngeal Airway (SLIPA).

SPECIFIC DEVICES

Laryngeal Tube (King LT and King LTS)

Description: The LT is a blindly placed SGA containing two balloons, or cuffs, one superior, and one inferior, to the glottic opening (Fig. 28-1A, B). It is designed to fit with the distal (inferior) balloon in the esophagus, sealing this off, and the proximal (superior) balloon in the posterior pharynx, posterior to the base of the tongue and epiglottis. Inflation of 20 to 90 cc of air at a single pilot balloon fills both cuffs simultaneously, creating a seal of approximately 60 cm H₂O proximal and distal to the glottis. Positive pressure ventilation can then be achieved through multiple apertures located between these cuffs. Obstruction does not appear to be a problem with the new King LTs, which have multiple ventilation apertures⁴ compared with earlier versions of the King tube. The most commonly used LT is the King LT, which was first created by VBM in Germany in 1998 and approved for use in the United States in 2003. The King LTS also has a separate lumen for suction, through which an orogastric tube can be passed. The LT is similar to the Combitube in many respects. Unlike the Combitube, however, it does not have an option of ventilating through two separate lumens.

This device is available in sizes 1 to 5:

Size	1	1.5	2	2.5	3	4	5
Weight	≤5	5-10	10-20	20-30	30-50	50-70	≥70 in kg

Evidence

Some practitioners feel that the LT is easier to insert than the Combitube and has a lower incidence of accidental laryngeal insertion because of its S shape. Additionally, its smaller size compared with the Combitube may be useful in patients with a smaller mouth opening. There have been several studies involving the LT, investigating time to and ease of placement, as well as leak pressures, in comparison with other SGAs.

FIGURE 28-1 A: King LT airway. B: King LT airway pictured in the airway with proximal and distal cuffs inflated.

Emergency use in field: In one study investigating use of SGAs by emergency medical technicians (EMTs) during field runs in a rural setting, the LT was placed on first attempt 12/13 times, and in some of these cases after failed attempts with ETT (6/13) and Combitube (3/13).⁵ In a larger study of both the King LTD and LTDS, emergency physicians and EMTs had a 98% success rate in placement. Furthermore, the time to placement in users who had 5 or less ETT insertions was: <45 seconds (n = 120), 46 to 90 seconds (n = 20), >90 (n = 7).⁶ In one study, the force to dislodge various airway devices in cadavers was measured. The ETT, LMA, and King airway required similar forces, whereas the Combitube required more force.⁷ This study may have relevance to patients in transport.

Use in the operating room: In a study of the King LT by experienced providers in operative cases with spontaneous ventilation, the ease of insertion was notable. The initial insertion time was <5 seconds in 98%, and 5 to 15 seconds in the remaining patients. Only 19% of these insertions required repositioning, whereas 2% required three trials at positioning. A relatively low incidence of sore throat was also described in this investigation, with 22% noted at 1 hour and 15% at 24 hours.⁸ In two other studies in humans comparing the LT with the Combitube, it was revealed that faster insertion times (39 vs 79 seconds) and more successful insertion (100% vs 87%) were possible with the LT than Combitube. There was no significant gastric insufflation observed in either case, but LT had a lower seal pressure (26 vs 36 cm H₂O).⁹,¹⁰ Several studies have compared the LT to LMA, and the authors found increased pressure required for leak with King LT, theoretically decreasing risk of gastric insufflation compared with the LMA.¹¹,¹²

Only gold members can continue reading. Log In or Register to continue