Write about Permeability Pulmonary Oedema here.

• In ARDS, it is thought that a cascade of inflammatory events arises over a period of hours from a focus of tissue damage

• Activated neutrophils aggregate and adhere to endothelial cells, releasing various toxins, oxygen radicals and mediators (e.g. arachidonic acid, histamine, kinins)

• This may be initiated by injuries or illnesses

• However, the outcome is endothelial damage resulting in Increased Alveolar Capillary Permeability

• Alveoli become filled with a protein-rich exudate containing abundant neutrophils and other inflammatory cells

• The airspaces show a rim of proteinaceous material - the hyaline membrane

• The characteristic feature of permeability pulmonary oedema in ARDS is that the Pulmonary Capillary Wedge Pressure (PCWP) is not elevated