The anatomical position of three extraglottic airway devices in patients with clear airways

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Abstract
Summary: We tested the hypothesis that, in patients with clear airways, the anatomical position of three single‐use extraglottic airway devices is similar. The airways studied were: the laryngeal mask airway unique (LMA‐U ™ ), the Softseal laryngeal mask airway (SS‐LM ™ ) and the Cobra perilaryngeal airway (Cobra‐PLA ™ ). Three hundred spontaneously breathing patients were randomly allocated to have their airway managed using one of these three supraglottic airway devices. A rigid endoscope was passed down the airway tube and the following anatomical assessments were made: position of the epiglottis; position of the glottis; and position of the cuff. The epiglottis was more frequently visible with the LMA‐U than with the SS‐LM (76 vs 57%, p = 0.006) and with the LMA‐U than with the Cobra‐PLA (76 vs 46%, p < 0.0001). The epiglottis was in contact with the mask aperture bars in 25% of patients, and in 34% of these, the epiglottis was seen to be herniated through the aperture bars. Herniation of the epiglottis through the mask aperture bars occurred more frequently with the Cobra‐PLA than the LMA‐U (8 vs 3%, p = 0.008). The vocal cords and arytenoids were more frequently visible with the LMA‐U and SS‐LM than with the Cobra‐PLA (both p < 0.006). Herniation of the arytenoids through the mask aperture bars was more frequently seen with the Cobra‐PLA than with the LMA‐U (8 vs 0%, p = 0.004). The position of the cuff was optimal for the LMA‐U and SS‐LM in 90% and 93% of patients, respectively. The cuff was more frequently in the midline with the LMA‐U than with the SS‐LM (p = 0.002). We conclude that the anatomical position of the LMA‐U and SS‐LMA is superior to that of the Cobra‐PLA in patients with clear airways. The mask aperture bars probably have no anatomical utility and predispose to herniation of the pharyngeal structures.

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