Cricoid-mental distance-based versus weight-based criteria for size selection of classic laryngeal mask airway in adults: a randomized controlled study

The optimal size selection of laryngeal mask airway (LMA) based on body weight is not always applicable. This study was prospectively conducted to evaluate the efficacy of cricoid-mental distance-based method versus weight-based method in optimal size selection of LMA in adults. Seventy-four patients (aged from 18 to 65) undergoing ophthalmic surgery were randomly assigned into cricoid-mental (CM) distance-based group or weight-based group to select appropriate size of LMA. The primary outcome was oropharyngeal leak pressure (OLP). Secondary outcomes included overall insertion success rate, number of insertion attempts, time to successful insertion, ease of insertion, score of fiber-optic view, peak inspiratory pressure during mechanical ventilation and postoperative pharyngolaryngeal morbidity. The OLP was significantly higher in CM distance-based group than that in weight-based group (19.38 ± 3.52 vs. 17.50 ± 3.18, P = 0.022). The successful placement at the first attempt in CM distance-based group was dramatically increased as compared with weight-based group (89.2% vs. 62.2%, P = 0.005). The overall success rate of LMA insertion in CM distance-based group was slightly increased in comparison with the weight-based group (100% vs. 91.9%, P = 0.240). There were no significant differences in score of fiber-optic view and postoperative pharyngolaryngeal morbidity between both groups (all P > 0.05). CM distance-based criteria is an alternative choice for optimizing size selection of classic LMA in adults.