Appropriate size of laryngeal mask airway for children

The aim of this crossover study was to determine the optimal size of laryngeal mask airway in children weighing 10 to 20 kg. In each of 67 apnoeic anaesthetized children, the size 2 and size 2 1/2 laryngeal mask airways were inserted consecutively by a skilled user and the cuff inflated to 60 cmH2O. Each LMA was assessed for the ease of insertion (by the number of attempts), oropharyngeal leak pressure, anatomical position (assessed fibreoptically) and the volume of air required to achieve intracuff pressure of 60 cmH2O. During the measurement of oropharyngeal leak pressure, the airway pressure was not allowed to exceed 30 cmH2O. There was no failed attempt at insertion with any size. The oropharyngeal leak pressure was significantly less for the size 2 LMA compared to the size 2 1/2 LMA (P < 0.001). The oesophagus was visible on three occasions, all with the size 2 LMA. Gastric insufflation occurred in three patients, all with the size 2 LMA. The incidence of low oropharyngeal leak pressure (< 10 cmH2O) was low (9.0%) and all occurred with the size 2 LMA. The fibreoptic bronchoscope scores were not significantly different between the two sizes of LMAs. The volume of air to achieve intracuff pressure of 60 cmH2O was much lower than the maximum recommended volume (5.1 ml for size 2 and 6.2 ml for size 2 1/2). We conclude that the size 2 1/2 LMA provides a better fit than size 2 in children 10 to 20 kg.