A comparison of the reinforced and standard laryngeal mask airway: ease of insertion and the influence of head and neck position on oropharyngeal leak pressure and intracuff pressure

Abstract

We conducted a randomized, crossover study of 60 paralysed anaesthetized adult patients to compare ease of insertion for the reinforced (RLMA) and standard laryngeal mask airway (LMA). We also test the hypothesis that oropharyngeal leak pressure (OLP) and intracuff pressure (ICP) vary with head and neck position for the two devices. OLP and ICP were documented in four head and neck positions (neutral first, then flexion, extension and rotation in random order) for each device. The size 5 was used for all patients and the ICP was set at 60 cm H2O in the neutral position. The first time insertion success rates were similar (LMA: 60/60 v RLMA; 59/60), but insertion time was slightly less for the LMA (6 v 8 s, P = 0.004). Compared with the neutral position, OLP for the LMA was higher in flexion (21 v 28 cm H2O, P < 0.0001) and rotation (21 v 23 cm H2O, P < 0.0001), but lower in extension (21 v 14 cm H2O, P < 0.0001). Compared with the neutral position, OLP for the RLMA was higher in flexion (19 v 27 cm H2O, P < 0.0001), similar in rotation (20 v 19 cm H2O), but lower in extension (27 v 14 cm H2O, P < 0.0001). The difference in OLP between flexion and extension was 13 and 14 cm H2O for the RLMA and LMA respectively. OLP was slightly higher for the LMA compared with the RLMA when the head was in neutral (P < 0.0001) and rotation (P < 0.0001), but was similar during flexion and extension. There was a significant positive correlation between ICP and OLP for the LMA (P < 0.0001) and RLMA (P < 0.0001). We conclude that ease of insertion is similar for the RLMA and LMA. OLP is higher with head/neck flexion and lower with extension for both devices and is associated with a similar change in ICP. We recommend assessing the efficacy of seal for all head and neck positions likely to be encountered prior to the start of surgery.