Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury.

Traditional approaches to mechanical ventilation use tidal volumes of 10 to 15 ml per kilogram of body weight. These volumes are larger than those in normal subjects at rest (range, 7 to 8 ml per kilogram), but they are frequently necessary to achieve normal values for the partial pressure of arterial carbon dioxide and pH. Since atelectasis and edema reduce aerated lung volumes in patients with acute lung injury and the acute respiratory distress syndrome, inspiratory airway pressures are often high, suggesting the presence of excessive distention, or “stretch,” of the aerated lung. In animals, ventilation with the use of large tidal volumes caused the disruption of pulmonary epithelium and endothelium, lung inflammation, atelectasis, hypoxemia, and the release of inflammatory mediators. The release of inflammatory mediators could increase lung inflammation and cause injury to other organs. Thus, the traditional approach to mechanical ventilation may exacerbate or perpetuate lung injury in patients with acute lung injury and the acute respiratory distress syndrome and increase the risk of nonpulmonary organ or system failure.