Acute Respiratory Distress Syndrome (ARDS)

n      may develop after a severe systemic illness or injury

n      sepsis, shock, burns, smoke inhalation, near-drowning, trauma, etc.

n      initial precipitating injury does not have to involve the lung

n      may develop 1-2 days after precipitating event

n      likely occurs as a result of severe systemic inflammatory response

n      massive production of circulating inflammatory cytokines

n      may have direct injury to lung (inhalational burns, etc.)

n      shock: lung ischemia because of ¯ perfusion

n      injury to alveolar wall and capillary membrane

n      increased permeability of capillary to fluid

n      fluid fills the alveoli ® impaired gas exchange ® hypoxemia

n      injury to surfactant-producing pneumocytes

n      ¯ surfactant production

n      ­ surface tension within alveoli (\alveoli want to collapse)

n      ¯ surfactant production

n      presence of fluid within alveoli (“dilutes” surfactant)

n      lungs become less compliant and “stiff”