(Fr: SDRA sur critères gazométriques PaO2/FIO2). ARDS picture. ARDS definition and grading at PMID 22797452. ARDS (and formerly ALI) are defined on the basis of gas exchange abnormalities. Thus, ARDS is not a well-characterized disease entity and may arise in widely disparate clinical scenarios. Pathologically, ARDS may correspond to DAD, pulmonary edema, acute NSIP-like ILD w/wo granulomas, -eosinophilic pneumonia (AEP), AFOP, amiodarone pulmonary toxicity, DAH, fat or silicone embolism, AIP, radiation injury, pulmonary fibrosis exacerbated by drugs or surgery (see under specific patterns) and drug- or alcohol-induced aspiration pneumonitis (see under XIg). Appropriate tests and BAL help exclude an infection and separate these entities. Mechanical ventilation and ECMO can be required in severe cases. Some patients respond to intravenous corticosteroid therapy. Review at PMID 1939859. See also under IL 'Diffuse Alveolar Damage', XIg, XVf and under 'Postoperative ARDS'