CXCL8 and acute respiratory distress syndrome: While blood has been the most common biological sample used to search candidate biomarkers, bronchoalveolar lavage (BAL) fluid is the closest sample to the site of injury and more accurately reflects the local lung environment [8], as illustrated by a pioneer study that identified BAL fluid—but not plasma—levels of IL-8 to predict ARDS development in at-risk patients [9].