For patients with a condition called acute respiratory distress syndrome (ARDS), managing their fluid levels to achieve a negative balance helps to improve their outcomes. In the past, patients' fluid levels were monitored with central lines placed into the bloodstream. However, most patients are now managed without central lines. A device called a NICOM (noninvasive cardiac output monitor) which monitors patients' heart function, using a few patches which are attached to their chest, may be useful in managing fluid levels without central lines. This study will compare the fluid balance in patients who are managed with typical care to the fluid balance in patients who are managed with the NICOM device.