Pharyngeal Mucosal Pressures, Airway Sealing Pressures, and Fiberoptic Position with the Intubating versus the Standard Laryngeal Mask Airway

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Abstract
Background: The tube of the intubating laryngeal mask (ILM) is more rigid than the standard laryngeal mask airway (LMA), and the authors have tested the hypothesis that pharyngeal mucosal pressures, airway sealing pressures, and fiberoptic position are different when the two devices are compared. Methods: Twenty anesthetized, paralyzed adults were randomly allocated to receive either the LMA or ILM for airway management. Microchip sensors were attached to the size 5 LMA or ILM at locations corresponding to the pyriform fossa, hypopharynx, base of tongue, posterior pharynx, and distal and proximal oropharynx. Mucosal pressures, airway sealing pressures, and fiberoptic positioning were recorded during inflation of the cuff from 0 to 40 ml in 10-ml increments. Results: Airway sealing pressures were higher for the ILM (30 vs. 23 cm H2O), but epiglottic downfolding was more common (56% vs. 26%). Pharyngeal mucosal pressures were much higher for the ILM at five of six locations. Mean mucosal pressures in the distal oropharynx for the ILM were always greater than 157 cm H2O, regardless of cuff volume. There was no correlation between mucosal pressures and airway sealing pressures at any location for the LMA, but there was a correlation at three of six locations for the ILM. Conclusions: The ILM provides a more effective seal than the LMA, but pharyngeal mucosal pressures are higher and always exceed capillary perfusion pressure. The ILM is unsuitable for use as a routine airway and should be removed after its use as an airway intubator.