Optimal size selection of laryngeal mask airway in Malaysian female adult population

The summary of various studies done looking at size selection of the laryngeal mask airway (LMA) in adults is that, selection based on sex is appropriate, and that both sizes 4 or 5 are adequate for adult females. However, in our local population these sizes may be too large especially the size 5 for adult females. To determine the optimal size of LMA in Malaysian female adults. 135 ASA 1 or 2 adult female patients coming for elective surgery, requiring general anaesthesia suitable for LMA insertion were randomised into 3 groups to receive either a size 3, 4 or 5 LMA. Optimal size of the LMA was assessed based on 4 parameters, the number of attempts at placement, the oropharyngeal leak pressure (OLP), fibre optic score and the percentage of the vocal cords seen. The 3 groups were demographically similar. There was no difference in the 3 groups in terms of number of attempts of placement, OLP and fibre-optic score. The percentage of vocal cords seen with the size 3 LMA was significantly less than for the size 4 and size 5 (p = 0.009). For the size 5 LMA group in 10/45 patients, the size 5 LMA was too big making it incorrectly positioned after successful insertion and in another 3/45 patients it was difficult to pass the size 5 LMA past the open mouth during insertion. There were no such problems with the size 3 or 4 LMA groups. The optimal size of LMA for the female Malaysian adult is size 4.