Abstract
Mechanical ventilation (MV) is critical for survival of many patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS). However, MV can also cause ventilator-induced lung injury (VILI) which may delay or prevent recovery of some patients. Experimental models demonstrated that VILI could be reduced by modifying traditional MV approaches. Some clinical trials demonstrated improved clinical outcomes in patients who received lower tidal volumes and inspiratory airway pressures to prevent VILI from overdistention. Experimental models suggest that VILI may occur from cyclic opening and closing of small bronchioles and alveoli, and that this can be reduced by applying positive end-expiratory pressure (PEEP). Some clinical studies suggested that clinical outcomes may be improved with the use higher levels of PEEP than are used with traditional MV strategies. However, in these studies higher PEEP was combined with lower tidal volumes and inspiratory airway pressures. It is not yet clear that higher PEEP improves clinical outcomes independent of volume-and-pressure limited MV strategies. The use of non-invasive MV may improve clinical outcomes in selected patients with ALI/ARDS. The physiologic rationale for using high frequency ventilation is strong, but clinical trials are needed to demonstrate improved clinical outcomes with high frequency ventilation when compared to lung-protective MV strategies.