抄録
Three types of laryngeal mask airway (LMA) are commercially available and include the standard laryngeal mask airway (sLMA), flexible laryngeal mask airway (fLMA), and intubating laryngeal mask airway (iLMA) . The three types of LMA are a similar shape and are comprised of almost identical materials apart from the tubing. Differences in tubing construction between the three types of LMA result in differences in physical characteristics. In the present study, the oropharyngeal leak pressure and fiberoptic bronchoscopy score of the three types of LMA was investigated in 20 patients. Patients were fitted with each type of LMA alternately in random order. The position of the LMA was observed using the following fiberoptic scoring system: 4, only vocal cords visible; 3, vocal cords plus posterior epiglottis visible; 2, vocal cords plus anterior epiglottis visible; 1, vocal cords not seen. Oropharyngeal leak pressure was measured in two body positions: the frontal position, with the face pointed forward and tilted upward, and the tilted position, with the head turned 45 degrees to the right. In both body positions, the number of patients with the highest fiberoptic score of 4 was significantly greater for the iLMA than for the sLMA or fLMA (p < 0.05) . The oropharyngeal leak pressure was significantly higher for the iLMA than for the sLMA or fLMA (p < 0.05) . The alterations in oropharyngeal leak pressure were smaller after changing body position for the iLMA than for the sLMA or fLMA. There was no significant correlation between fiberoptic score and oropharyngeal leak pressure for any LMA, except for the fLMA in the frontal position (p < 0.05) . The differences in oropharyngeal leak pressure and fiberoptic score between the three types of LMA investigated in the present study result from the properties of the LMA tube as the other mask characteristics are similar. The material and shape of the LMA tubing should be carefully considered to maximize oropharyngeal leak pressure.
