The Influence of Head and Neck Position on Oropharyngeal Leak Pressure and Cuff Position with the Flexible and the Standard Laryngeal Mask Airway

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Abstract
We conducted a randomized, cross-over study of 20 paralyzed anesthetized adult patients to test the hypothesis that oropharyngeal leak pressure and cuff position (assessed fiberoptically) vary with head and neck position for the flexible (FLMA) and standard laryngeal mask airway (LMA). Both devices were inserted into each patient in random order. Oropharyngeal leak pressure and fiberoptic position (including degree of rotation) were documented in four head and neck positions (neutral first, then flexion, then extension and rotation in random order) for each device. The size 5 was used for all patients, and the intracuff pressure was set at 60 cm H2 O in the neutral position. All airway devices were inserted at the first attempt. Oropharyngeal leak pressure was similar for the FLMA and LMA in the neutral (22 vs 21 cm H2 O), flexed (26 vs 26 cm H2 O), and extended positions (19 vs 18 cm H2 O) but was slightly higher for the LMA when the head was rotated (19 vs 22 cm H2 O; P = 0.04). Compared with the neutral position, oropharyngeal leak pressure for the LMA was higher with flexion (26 vs 21 cm H2 O; P = 0.0004) and lower with extension (18 vs 21 cm H2 O; P = 0.03) but similar with rotation. Compared with the neutral position, oropharyngeal leak pressure for the FLMA was higher with flexion (26 vs 22 cm H2 O; P = 0.0001) and lower with extension (19 vs 22 cm H2 O; P = 0.03) and rotation (19 vs 22 cm H2 O; P = 0.03). The difference in oropharyngeal leak pressure between flexion and extension was 7 and 8 cm H2 O for the FLMA and LMA, respectively. Fiberoptic position was similar between devices and was unchanged by head and neck position. Rotation was not detected fiberoptically. We conclude that there are small changes in oropharyngeal leak pressure but no changes in cuff position in different head and neck positions for the FLMA and LMA. Oropharyngeal leak pressure may be improved by head and neck flexion and by avoiding extension. Implications: There are small changes in oropharyngeal leak pressure but no changes in cuff position in different head and neck positions for the flexible and standard laryngeal mask airways. Oropharyngeal leak pressure may be improved by head and neck flexion and by avoiding extension. (Anesth Analg 1999;88:913-6)