The investigators test the hypothesis that there is an increased risk of ARDS in patients with heritable traits relating to inflammatory cytokines and surfactant. They are examining risk and prognosis, and examining case and control genetics in relation to cytokine levels. They also plan to do a case-series analysis from a separate study of the ARDS network. They will examine TNF alpha and beta, interleukin-1 receptor antagonist, surfactant protein B and interleukin-10 (IL-10).