There are two techniques of airway suction during invasive mechanical ventilation in patients with acute respiratory distress syndrome (ARDS): open airway suction and enclosed airway suction. To do the former, patients are disconnected from ventilators in the airway suction, and suction tubes are put into the endotracheal tubes to suck; to do the latter, patients will not be disconnected from ventilators. Positive end-expiratory pressure (PEEP) ventilation is one of the main measures to improve oxygenation. When open endotracheal suction is performed, disconnection of PEEP leads to alveolar collapse. It may increase shunt effect, dead cavity ventilation, and ventilation/perfusion mismatch, and further aggravate lung injury. In this paper, we analyze the shunt, dead cavity, ventilator-related lung injury, and hemodynamics, and explore the endotracheal suction technique for lung protection in ARDS.