THE SPATIAL-DISTRIBUTION OF PULMONARY-LESIONS IN SEVERE ARDS - AN AUTOPSY STUDY OF 35 CASES

The present study was undertaken in order to describe the local distri bution and temporal course of pulmonary lesions in severe ARDS. We inv estigated a total of 35 patients (22 females), ranging in age from 2 t o 51 years, who suffered from ARDS III and IV and were treated by extr acorporeal CO, removal and low frequency positive pressure ventilation (ECCO2-R). The extent of acute and chronic diffuse alveolar damage wa s assessed on histologic gross sections in the ventral, central and do rsal zone of the upper and lower lobes. The lesions showed a character istic uniform distribution. Areas with chronic DAD were predominantly situated in the ventral portions of the upper lobes. Acute DAD predomi nated in the dorsal and basal areas of the lung. The extent of acute a nd chronic DAD was virtually independent of the duration of disease. H emorrhage occurred at the interface zone between chronic and acute DAD and made up a significant volume portion of the lung tissue, ranging between 8% (lower lobes) and 42% (upper lobes). We conclude that the p rogression of acute DAD to chronic DAD is mainly determined by local f actors (hydrodynamic and hydrostatic forces, intraalveolar pressure) t hat differ within the lung, whereas the duration of disease plays a mi nor role. Parenchymal hemorrhage occurs at the interface between areas of acute and chronic DAD and may therefore primarily be due to an inc reased susceptibility of the pulmonary parenchyma to mechanical stress .