Diagnostic criteria for adult respiratory distress syndrome: time for reappraisal.

To assess whether current diagnostic criteria for the adult respiratory distress syndrome (ARDS) may limit research to patients with a range of severity of respiratory failure and risk factors for ARDS were studied. In 28 patients ARDS did not develop; in 9 it did; and the other 13 met the diagnostic criteria at their first assessment. Plasma concentration of neutrophil elastase-alpha 1-antitrypsin complex was higher in all groups than in controls. For all patients, plasma elastase-complex was related to worsening hypoxia and to increased bronchoalveolar lavage protein content. Elastase-complex was present in all bronchoalveolar lavage samples and was related to protein content and differential neutrophil counts. Patients at risk of or with ARDS had a spectrum of respiratory failure to which intravascular and intra-alveolar neutrophil elastase release and capillary permeability were related. This suggests that the state recognised as ARDS is not a distinct pathophysiological entity.