Work of Breathing and Mechanical Ventilation in Acute Lung Injury

The primary goal of this study is to measure changes in biological markers of inflammation in critically-ill patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) while they are treated with different styles of lung-protective, artificial breathing assistance. Secondary goals are to measure the breathing effort of patients using different artificial breathing patterns from the breathing machine. The primary hypothesis is that volume-targeted artificial patterns will produce less inflammation. The secondary hypothesis is that volume-targeted artificial patterns will increase breathing effort compared to pressure-targeted artificial patterns.