Objective To investigate new methods in preventing ventilator-induced lung injury.Methods One hundred and eighty patients undergoing assist-control ventilation(ACV) were randomly divided into three groups,60 cases in each.Patients in group A first received volume controlled ACV with constant flow waveform mode,then changed to decelerating flow waveform mode.Patients in group B experienced volume-controlled ACV with constant flow waveform mode.In group C,pressure controlled ACV was used.The inspiratory press...