adult respiratory distress syndrome (ards)

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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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