 After screened for preoperative risk classification of postoperative respiratory complications,360 patients undergoing elective neurosurgery are randomly assigned to two groups, lung-protective ventilation L and traditional ventilationT.Patients are mechanical ventilated with either a tidal volume of 10-12 mlkg ideal body weight IBW,T or 6-8mlkg IBW with 6-8 cm H2O PEEPL,both with recruitment maneuver RM.Each RM consists of applying a continuous positive airway pressure of 30 cmH2O for 30 seconds. Postoperative pulmonary complications are compared between groups. 