There are a wide range of problems which make certain PICU patients more likely to develop either ALI or ARDS. This research aims to determine which of these children are at the greatest risk for ALI/ARDS by examining differences in plasma biomarkers and in DNA of a large number of PICU patients. We are hypothesizing that significant differences in the level of specific plasma biomarkers or in the frequency of specific DNA variants exist in children who develop ALI/ARDS.