{"id":6640,"date":"2021-09-13T21:04:46","date_gmt":"2021-09-13T19:04:46","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/pathology\/respiratory-system\/ards-2\/"},"modified":"2021-09-13T21:05:17","modified_gmt":"2021-09-13T19:05:17","slug":"ards-2","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/pathology\/respiratory-system\/ards-2\/","title":{"rendered":"ARDS"},"content":{"rendered":"\n

Also known as adult <\/strong>respiratory distress syndrome.<\/p>\n\n\n\n

1<\/sup>Definition<\/h4>\n<\/span>\n\n\n

An acute respiratory failure is associated with inflammation.<\/p>\n\n\n<\/span>\n

Clinical definition1<\/sup><\/h4>\n<\/span>\n\n\n

The Berlin definition requires all four criteria to be present for the diagnosis of ARDS:<\/p>\n\n\n\n

  1. Time — Within a week of a known clinical insult<\/li>
  2. Chest imaging — Bilateral opacities consistent with pulmonary edema<\/li>
  3. Origin of edema — Not fully explained by cardiac failure or fluid overload<\/li>
  4. Oxygenation — Impaired oxygenation<\/li><\/ol>\n\n\n<\/span>\n

    General mechanism<\/h4>\n<\/span>\n\n\n

    An acute insult to the airways leads to an inflammatory reaction, resulting in the destruction of alveoli.<\/p>\n\n\n<\/span>\n

    Cellular mechanism<\/h4>\n<\/span>\n\n\n

    The mechanism is based on the cellular reaction during acute inflammation:<\/p>\n\n\n\n

    1. An acute insult causes the release of IL-8 and other cytokines (TNF, IL-1) by alveolar macrophages<\/li>
    2. Endothelial activation and recruitment of neutrophils by chemotaxis<\/li>
    3. The neutrophils activate and release their products, causing alveolar damage:
      1. Epithelial and endothelial damage causing alveolar edema<\/li>
      2. Loss of surfactant<\/li><\/ol><\/li>
      3. The damage results in necrosis and formation of hyaline membranes <\/strong>composed of the necrotized cells, edema fluid, and CT fibers<\/li>
      4. At the end of the repair (organizing phase), type II pneumocytes proliferate rapidly in order to regenerate the alveolar lining
        1. Recall that type I pneumocytes are the squamous cells that line the alveoli, and they are unable to proliferate<\/li>
        2. Usually, the repair is unsuccessful, due to CT deposition, and the end result is intra-alveolar fibrosis<\/li><\/ol><\/li><\/ol>\n\n\n<\/span>\n

          Characteristics<\/h4>\n<\/span>\n\n\n