The traditional approach in patients with ALI/ARDS is to ventilate using tidal volumes between 10 and 15 ml/kg body weight, almost twice the average tidal volume at rest (7-8 ml/kg body weight), and to maintain a low positive endexpiratory pressure (PEEP). The purpose of this approach is to achieve normal values for the pH and partial pressure of arterial carbon dioxide. However, this method leads to high inspiratory airway pressures and to excessive stretch of the aerated lung.