definition of ARDS

Berlin definition

acute diffuse, inflammatory lung injury
increased pulmonary vascular permeability, increased lung weight, and loss of aerated lung tissue
hypoxemia and bilateral radiographic opacities,
associated with increased venous admixture, increased physiological dead space and decreased lung compliance.

acute onset (within 1/52)
not exclusively or primarily attributable to cardiogenic pulmonary edema/fluid overload
radiologic evidence:
- Bilateral opacities on chest radiography and computed tomography or
- bilateral B lines and/or consolidations on ultrasound not fully explained by effusions, atelectasis, or nodules/masses

P/F ratio

Injury
Exudative – alveolar capillary membrane disruption with inflammatory cell infiltrate and high protein exudate to form hyaline membranes → damage to alveolar-capillary barrier => pulmonary oedema
Proliferative – proliferation of abnormal Type II alveoli cells and inflammatory cells
Fibrotic – infiltration with fibroblasts which replace alveoli and alveolar ducts with fibrosis
Resolution – slow and incomplete repair and restoration of architecture