Lung structure and function in different stages of severe adult respiratory distress syndrome

Objective. - To assess the clinical consequences of duration of adult respiratory distress syndrome (ARDS) on lung structure and function. Design. - Retrospective analysis. Setting. - A university hospital referral center for extracorporeal support. Patients. - A total of 84 patients with severe ARDS (Murray score >2.5) recruited from 48 intensive care units (1979 to 1992), who suffered ARDS and underwent mechanical ventilation for up to 1 week (37 patients with early ARDS), between 1 and 2 weeks (24 patients with intermediate ARDS), or more than 2 weeks (23 patients with late ARDS) and subsequently underwent extracorporeal support. Main Outcome Measures. - Before beginning extracorporeal support, we measured gas exchange, pulmonary mechanics, hemodynamics, oxygen transport and delivery, incidence of barotrauma (presence of one or more thoracic tubes for pneumothorax drainage), and organ dysfunctions. In a subgroup of 16 patients, we studied lung structure by computed tomographic scan, scoring the densities and quantifying the emphysemalike lesions (bullae). Results. - Late ARDS showed lower respiratory compliance, higher dead space, higher PaCO₂, lower venous admixture, and lower positive end-expiratory pressure requirement compared with early ARDS (P