The Influence of Mouth Opening on Oropharyngeal Leak Pressure, Intracuff Pressure, and Cuff Position With the Laryngeal Mask Airway

PurposeThe aim of this study was to investigate the influence of mouth opening on oropharyngeal leak pressure, intracuff pressure, and cuff position of the laryngeal mask airway (LMA).Patients and MethodsFifteen patients who were scheduled for elective oral surgery were recruited into this study. A single, experienced LMA user inserted the LMA according to the manufacturer's recommended technique. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were documented under 3 mouth conditions: neutral position (1.4-cm distance between upper and lower incisors), mouth open (5- to 6-cm distance between upper and lower incisors), and return to the neutral position. Any ventilation difficulties under the 3 mouth conditions were recorded.ResultsOropharyngeal leak pressure with the mouth open was higher than in the neutral position (P < .001). Compared with the neutral position, intracuff pressure was also higher with the mouth open (P < .001). Both measurement values returned to control levels when the neutral position was once again assumed. The LMA position observed by fiberoptic bronchoscopy was unchanged by mouth opening and was similar in the 3 mouth conditions (P = .998). Although ventilatory difficulties occurred after mouth opening in 8 of 15 patients (P < .001), it did not occur when the neutral position was reassumed.ConclusionsThis study showed that mouth opening led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution because gastric insufflation, sore throat, and ventilation difficulties may occur.