P ulmonary
Aliya N. Husain, M.D.
IV. Adult Respiratory Distress Syndrome (Diffuse Alveolar Damage)
  1. ARDS is the end result of acute alveolar injury caused by a variety of insults and probably initiated by different mechanisms. The initial injury is to either the capillary endothelium or alveolar epithelium. There is increased capillary permeability, interstitial and then alveolar edema, fibrin exudation and formation of hyaline membranes. Organization and scarring follows.

  2. The capillary defect is produced by an interaction of inflammatory cells and mediators, including leucocytes, cytokines, oxygen radicals, complement and arachidonate metabolites, that damages the endothelium and allows fluid and proteins to leak. Endotoxin, neutrophils and macrophages may also play key roles in the pathogenesis of ARDS.