Respiratory support is the basis of the treatment of acute respiratory distress syndrome (ARDS).Recent researches have shown that application of protective lung ventilation with low tidal volume can improve significantly the symptoms and prognosis of ARDS patients.However,low tidal volume is not conducive to recruitment of collapse alveolus.Therefore,it is necessary to keep the lung open using protective lung ventilation combined with recruitment maneuvers.However,the efficacy of recruitment depends on many factors,including the etiology of ARDS,courses,recruitment maneuvers or the ventilation parameters before recruitment,tidal volume and PEEP level after recruitment and so on.