• The blue arrows point to the type II pneumocytes which are very prominent; their nuclei protruding into the alveolar space.
• The arrows highlight the thickened septum.
• The septum contains excess collagen, fibroblasts, and lymphocytes.
• Hyaline membranes are not present.
|Adult Respiratory Distress Syndrome|
• Result of diffuse capillary damage in the lung with capillary leak
• Endothelial cell damage (direct, secondary to inflammatory cells and mediators esp neutrophils, due to endotoxin)
• Capillary leak into the alveolae with accumulation of edema and proteinaceous, necrotic material that forms hyaline membranes
• Edema interferes with gas exchange
• Direct toxicity due to smoke inhalation, drugs etc.
• Secondary effect of profound hypoxia and circulatory failure
• Sequel to severe trauma or other life threatening condition
• Rapid development of profound respiratory failure
• Fatality rate is high.
|General Gross Description|
• Heavy lungs which are deep reddish purple and stiff
|General Micro Description|
• Congestion of the vessels and proteinaceous acellular edema in the alveolae
• Accumulation of vividly eosinophilic, acellular hyaline membranes against alveolar septae
• Organize into circular fibrous swirls which over time replace alveoli
• Occasionally resolve completely
• Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th edition. Philadelphia, W.B. Saunders, 1994, pp. 676-678.