Fibroproliferation in Late Adult Respiratory Distress Syndrome: Pathophysiology, Clinical and Laboratory Manifestations, and Response to Corticosteroid Rescue Treatment

Abstract

A dult respiratory distress syndrome (ARDS) is a dynamic disease that rapidly progresses into phases with different clinicopathophysiologic characteristics and different therapeutic needs. Late ARDS refers to the clinical stage of ARDS when the lung attempts to repair the initial or persistent injury to the endothelial and epithelial lining of the respiratory units. Its histologic correspondent is termed fibroproliferative phase which, if unhalted, leads to extensive fibrosis. Pulmonary fibroproliferation is a stereotypic reparative reaction to tissue injury characterized by the replacement of damaged epithelial cells and the striking accumulation of mesenchymal cells and their connective tissue products in the airspaces and walls of the intra-acinar microvessels. 1 Meduri GU Late ARDS New Horizons. 1993; 1: 563-577 PubMed Google Scholar Its evolution is determined by the extent of initial inflammatory reaction in the lung (alveolar denudation, basement membrane destruction, and quantity of intraalveolar exudate) and by the presence of a protracted inflammatory response (with or without control of the cause of ARDS). 2 Headley S Meduri GU Stentz F et al. Unfavorable outcome in patients with ARDS is related to persistent release of inflammatory cytokines [abstract]. Chest. 1993; 104: 154S Google Scholar , 3 Burkhardt A Alveolitis and collapse in the pathogenesis of pulmonary fibrosis. Am Rev Respir Dis. 1989; 140: 513-524 Crossref PubMed Scopus (143) Google Scholar Fibroproliferation is a diffuse process, as indicated by the findings of computed tomography, gross inspection at surgery, and microscopic analysis of biopsy specimens from different lobes. 1 Meduri GU Late ARDS New Horizons. 1993; 1: 563-577 PubMed Google Scholar Regional heterogeneity, however, exists, 1 Meduri GU Late ARDS New Horizons. 1993; 1: 563-577 PubMed Google Scholar and at histologic examination, focal areas of normal parenchyma are occasionally found. 1 Meduri GU Late ARDS New Horizons. 1993; 1: 563-577 PubMed Google Scholar