ObjectiveTo evaluate the influence of the depth of muscle relaxation on airway seal using ProSealLaryngeal Airway (PLMA) and Classic Laryngeal Mask Airway (CLMA) during radical mastectomy.MethodsSixty ASA Ⅰ or Ⅱ patients aged 30~60 years, body mass index less than 30 kg/m2 undergoing radical mastectomy were enrolled in the study.The patients were randomized to receive either PLMA ventilation (group P) or CLMA ventilation (group C) (n=30 each), and we used the fiberoptic bronchoscopy to adjust positions.In group C, after insertion, the cuff pressure was set at 60 cmH2O .Both groups used total intravenous anesthesia and intermittent positive pressure ventilation.The depth of muscle relaxation determined with TOFWatch SX monitor.The oropharyngeal leak pressure（OLP）was measured when the TOF ratio was 0(T1), 20%(T2), 40%(T3), 60%(T4) and 80%(T5).The incidence of gastric distension during the operation was recorded.ResultsThere was no significant difference in OLP at T1~T5 between two groups.The OLP was decreased at T4~T5 in group P and at T3~T5 in group C as compared with the value at T1.There was no obviously gastric distension and other complications during operations in both groups.ConclusionThe depth of muscle relaxation can affect airway seal using PLMA and CLMA.We can get better sealing effect when there is better muscle relaxation.