ARDS: A Clinical Syndrome or a Pathological Entity?

Abstract

Despite substantial advances in the understanding of the pathogenesis of the acute respiratory distress syndrome (ARDS), no specific pharmacologic treatment has been shown to affect outcome. This failure has been attributed in part to a lack of a reliable definition for ARDS. Indeed, how the target population is defined for a clinical trial affects the results and their generalizability. Studies including patients with a low probability of responding to the treatment under study (because they are unlikely to have the diagnosis or because of other reasons) are likely to yield false-negative results. Thus a reliable definition of ARDS is essential for research (clinical trials, epidemiologic studies, and studies on pathogenesis) and for clinical practice (to reliably make a diagnosis of ARDS and provide appropriate treatment). In this context several relevant questions arise: What are the different diagnostic criteria for the definition of ARDS? What are the diagnostic test characteristics of these different criteria considering diffuse alveolar damage (DAD) as the histological reference for the diagnosis of ARDS? Does the clinical phenotype of ARDS correlate with one or with more histological entities? Is DAD the sole histological manifestation of ARDS?