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Laryngeal Tube

The Laryngeal Tube (LT) and its American variant the King LT™ are supraglottic airway devices that have met with recent interest in the airway community (Figures 10 and 11). Created as an alternative to tracheal intubation or mask ventilation, this product was designed to permit positive pressure ventilation as well as to allow for spontaneously breathing patients. The LT consists of a large bore tube with a large asymmetric balloon cuff at its middle part (proximal cuff) and a small balloon cuff located at the tip (distal cuff). There are two distal apertures in the tube between the two cuffs, through which gas movement takes place. A new version of the LT with a gastric drain is now nearing commercialization.

One theoretical advantage of the LT has been described by Hagberg et al. [27]:
“A known disadvantage of the LMA is its inability to protect the airway from the aspiration of gastric contents. Assuming an adequate seal, the distal esophageal cuff provides an invaluable means of airway protection. By blocking the opening of the esophagus, the King LT ™ should minimize the risk of aspiration. Our study supports this concept, albeit in a small number of patients, as there were no incidences of regurgitation or aspiration.”

In a comparative study by Cook et al. [28], 72 patients were randomly allocated to receive either the LT (n=36) or an LMA (n=36). The investigators compared the adequacy of controlled ventilation during anesthesia, leak pressure and the incidence of postoperative complications. They found that insertion was successful within 2 attempts in all 36 patients for the classic LMA and in 35 patients for the laryngeal tube. The mean leak pressure for the LT (28 cm H2O) was significantly greater than that for the classic LMA (21 cm H2O. Ventilation was classified as “good” in 25 cases, “fair” in 11, and “failed” in no patients with the classic LMA; and “good” in 23, “fair” in 11 and “failed” in two for the LT. There were no significant differences in adequacy of ventilation or in the incidence and severity of any postoperative complications. The authors concluded that the LT was "as effective as the classic LMA at providing a patent airway during controlled ventilation of the lungs, and that the laryngeal tube gave a significantly greater sealing pressure than the classic LMA".

Figure 9. Laryngeal Tube placement diagram

Figure 9. Correct anatomical placement of the Laryngeal Tube. From [29].

Figure 10. Laryngeal tube King LT and view of ventilatory holes

Figure 10.  Left: The King LT™ Right: View of ventilatory holes of the King LT™ (main oval-shaped apertures and 2 lateral ventilatory openings [arrows]). Figure 10 and figure legend from [27].

Brimacombe et al. [30] compared the LMA ProSeal (PLMA) and the laryngeal tube (LT) in 120 anesthetized and paralyzed patients with respect to: 1) insertion success rates and times, 2) seal quality, 3) ventilatory variables with pressure-controlled ventilation, 4) tidal volume in different positions, and 5) airway interventional requirements. The criteria for an effective airway included an expired tidal volume at or over 6 mL/kg during pressure-controlled ventilation at 17 cm H2O with no leak and no gastric insufflation. First attempt success rates were similar (PLMA: 85% vs. LT: 87%), but the oropharyngeal leak pressure was larger for the PLMA at 50% maximal recommended cuff volume, while it was similar at the maximal recommended cuff volume. The authors found that the number of airway interventions was smaller for the PLMA and that airway obstruction was more frequent with the LT. Based on these and other results the authors concluded that the PLMA offers advantages over the LT in paralyzed patients undergoing pressure-controlled ventilation.

 

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