adult respiratory distress syndrome (ards)
DESCRIPTION
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ADULT RESPIRATORY DISTRESS SYNDROME
Non-cardiogenic pulmonary edema
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ARDS - DEFINITION Severe arterial hypoxemia
Partial pressure arterial oxygen/fraction of inspired oxygen [Pao2/Fio2] ratio of 200 or less
Bilateral alveolar infiltrates No elevated left atrial pressure
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Pulmonary wedge pressure Should be normal in ARDS > 18mmHg
Cardiac failure
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Pathophysiologic hallmark of ARDS Increased vascular permeability
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Diffuse damage to the alveolar capillary membrane Increased vascular permeability Fluid accumulation inside the alveoli Loss of diffusion capacity Surfactant abnormalities
Damage to type 2 pneumocytes
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Initial injury Capillary endothelium
Alveolar epithelial cells More resistant than vascular endothelial
cells to injurious effects
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Vital to the causation of ARDS Diffuse alveolar capillary damage
Caused by a variety of insults
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PATHOLOGICAL CHANGES
Diffuse pulmonary capillary damage
Diffuse alveolar damage Protein rich edema fluid in the
alveoli Hyaline membrane formation
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Failure of alveolar capillary membrane function Flooding of the alveoli with protein
rich edema fluid
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Surfactant loss and dysfunction Alveolar collapse
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Diffuse lung tissue destruction and exudation Cannot be easily resolved Organization with scarring
Chronic lung disease
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FOUR MOST COMMON CAUSES OF ARDS Sepsis Diffuse pulmonary infections
Viral Mycoplasma Pneumocystis pneumonia Miliary tuberculosis
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