Acute Respiratory Distress Syndrome Definition and Pathology

Pathological Hallmarks

The pathological hallmark of ARDS is diffuse alveolar damage, which evolves through distinct phases, including an early exudative phase, a fibroproliferative phase, and a fibrotic phase, characterized by interstitial swelling, proteinaceous alveolar edema, hemorrhage, fibrin deposition, hyaline membrane formation, type II pneumocyte proliferation, mononuclear cell infiltration, and collagen deposition 1

The Ashbaugh definition established ARDS as a distinct clinical syndrome with specific pathophysiological mechanisms, including leukocyte infiltration, increased pulmonary vascular permeability, and loss of aerated lung tissue, as noted by the European Respiratory Review 2
The lack of specificity in the Ashbaugh definition contributed to decades of failed therapeutic trials due to heterogeneous patient populations, emphasizing the need for precision medicine approaches that account for the syndrome's inherent heterogeneity, as highlighted by the European Respiratory Review 2, 3