Water flow between the upper esophagus and pharynx for the LMA and COPA in fresh cadavers. Laryngeal mask airway, and cuffed oropharyngeal airway.

Abstract

In this randomised, crossover cadaver study, we determine the esophageal pressure (EP) at which water flow occurs between the upper esophagus and pharynx for the laryngeal mask airway (LMA) and cuffed oropharyngeal airway (COPA). Ten male and ten female cadavers were studied. The infusion set of a pressure controlled, continuous flow pump was inserted into the upper esophagus and ligated into place. The EP was increased in 2 cm H2O increments. This was performed without an airway device (controls) and over a range of cuff volumes for the LMA (0-40 ml) and COPA (0-60 ml). Regurgitation pressure (RP) was the EP at which fluid was first seen with a fibreoptic scope in the hypopharynx (controls) and above or below the cuff (LMA and COPA). The RP was higher for the LMA than for the COPA and controls (P<0.0004), and RP was similar for COPA and controls. There was an increase in RP with increasing cuff volume for the LMA from 0 to 10 ml (P<0.0001). There were no increases in RP with increasing cuff volume for the COPA. The EP at which fluid leaked above and below the cuff was similar for the LMA at all cuff volumes. The EP at which fluid leaked above the cuff was higher than below the cuff for the COPA when the cuff volume was 40 ml (P<0.0001). In fresh cadavers, the LMA provides better airway protection from fluid in the upper esophagus than the COPA.