Calculated vs measured pharyngeal mucosal pressures with the laryngeal mask airway during cuff inflation: assessment of four locations

We have compared calculated with measured pharyngeal mucosal pressures at f our different locations on the surface of the laryngeal mask airway (LMA) d uring cuff inflation in 10 anaesthetized, paralysed adult patients. Microch ip sensors were attached to a size 5 LMA at the following locations: the an terior and lateral side, tip and backplate. Pressures were recorded during inflation of the cuff from 0 to 40 ml in 5-ml increments. Calculated pressu res were determined by subtracting in vivo from in vitro intracuff pressure s. Calculated pressures were greater than measured pressures at cuff volume s of 5 mi or greater at all locations (P less than or equal to 0.003). The greatest mean calculated and measured pressures were 118 and 14 cm H2O, res pectively. We conclude that measured mucosal pressures at the four location s tested were less than calculated pressures and less than capillary perfus ion pressure.