• pulmonary edemaFluid accumulation in air spaces and parenchyma of the lungs
    • leads to impaired gas exchange and may cause respiratory failure 
  • Pathophysiology
    • edema arises due to an imbalance in hydrostatic and/or oncotic pressure
      • increased hydrostatic pressure in the pulmonary capillaries (Pc)
        • cardiogenic causes (see below)
      • decreased oncotic pressure in the pulmonary capillaries (πc)
        • kidney or liver dysfunction (e.g. nephrotic syndrome, cirrhosis)
      • movement of fluid is driven by Starling forces
  • Causes
    • changes in pressure are of cardiogenic or non-cardiogenic origin
    • cardiogenic causes include
      • heart failure
        • left heart failure
        • volume overload
        • mitral stenosis
      • in all cases above, an increase in left ventricular end diastolic volume increases hydrostatic pressure in LV, LA, pulmonary vein, and pulmonary capillaries
        • the increase in hydrostatic pressure overwhelms the oncotic pressure in the pulmonary capillaries
        • a transudate leaks into the interstitial space and ultimately into the alveoli
    • non-cardiogenic causes include
      • infection
        • sepsis
        • pneumonia
      • aspiration
        • drowning
        • gastric aspiration
      • drugs
        • heroin
      • high altitude
      • ARDS
        • alveolar-capillary damage
  • Symptoms
    • dyspnea
      • including orthopnea and paroxysymal nocturnal dyspnea (PND)
  • Physical exam 
    • bibasilar inspiratory crackles
      • due to air expanding fluid-filled alveoli
    • rusty-colored sputum
      • due to rupture of pulmonary capillaries from elevated hydrostatic pressure
    • wheezing
      • due to peribronchiolar edema
      • "cardiac asthma"
  • CXR
    • congestion in upper lobes
    • perihilar congestion
      • "bat wing configuration"
    • alveolar infiltrates
    • Kerley's lines 
      • due to septal edema
  • Biopsy
    • hemosiderin-laden alveolar macrophages ("heart failure cells")
      • macrophages phagocytose blood following rupture of capillaries
  • Treat underlying condition
    • nitrates and diuretics used for cardiogenic causes
  • Respiratory support
    • Non-invasive positive pressure ventilation
    • supplemental oxygen 

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