Severe Acute Respiratory Distress Syndrome

**Semantic type:** Disease or Syndrome

**Definition:** A form of acute respiratory distress syndrome (ARDS) that is marked by severe hypoxemia. Based on the Berlin criteria, onset must occur within one week of a clinical insult or there must be evidence of new or worsening respiratory symptoms. Chest imaging reveals bilateral opacities consistent with pulmonary edema that are not fully explained by effusions, lobar/lung collapse, or nodules. Respiratory failure is not fully explained by heart failure or fluid overload and objective assessment, e.g. echocardiography, is required to exclude hydrostatic edema if no risk factor is present. Additionally, oxygenation as measured by a partial pressure of arterial oxygen (PaO2) to the fraction of inspired oxygen (FIO2) is equivalent to 100 mm Hg or less with positive end-expiratory pressure (PEEP) of at least 5 cm of water (Ranieri VM et al., JAMA. 2012;307(23):2526-2533). Severe ARDS may be associated with cytokine release syndrome.

**Synonyms:** - Severe ARDS