Stage
Stage
Histopathology
Exudative (1)
0-7days
- Acute inflammatory reaction in the lung caused by insult to the epithelium
- Alveoli fill with neutrophils, blood and a protein-rich pulmonary oedema (0.5)
- Associated alveolar epithelial and capillary endothelial damage, with loss of alveolar cells and structural integrity (0.5)
- Hyaline membranes form composed of cellular debris and plasma proteins (peak 4–5 days) (0.5)
- Destruction of the pulmonary vascular bed
- Dysregulation of coagulation and fibrinolysis leads to microthrombus formation
- Capillary thrombosis occurs (0.5)
(Max 1)
Proliferative (1)
7-14 days
- Proliferation of type II pneumocytes and fibroblasts (0.5)
- Fibrin deposition (0.5)
(Max 1)
Fibrotic (1)
>14 days
(Max 1)