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Pulmonary Edema
definition, phases
Abnormal accumulation of fluid in the extravascular spaces and tissues of the lung
- 1. Interstitial edema
- 2. Alveolar edema
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Pulmonary edema
Pathology
- Pathology:
- -Perivascular cuff of edema around pulmonary vessels:
- -Septal lines on CXR: horizontal white lines, perpendicular to the pleura:
No impairment of lung function with interstitial edema
- Alveolar edema:
- -Fluid in the alveolar space
- -CXR demonstrates (usually) bilateral, symmetric opacity that is most often worse at the base of the lungs:
"butterfly" or "bat" wing appearance
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Pulmonary Edema
pathogenesis
Starling equation: movement of fluid across a membrane
- NET FLUID OUT = K [ (Pc-Pi) -σ(πc-πi)]
- -hydrostatic pressures
- -osmotic pressures
-Continuous loss of fluid out of the capillaries into the interstitial space, eventually leaves via the lymphatics.
- Pathogenesis:
- 1. Increase in capillary hydrostatic pressure [Pc]
- (Increase in alveolar pressure causes compensatory increase in lymph flow)
- - myocardial infarction
- - hypertensive left ventricular failure
- - mitral stenosis
- - mitral stenosis
- - transfusion overload
- - pulmonary veno-occlusive disease
- 2. Increase capillary permeability [K, σ, πi]
- - inhaled or circulating toxins
- - adult respiratory distress syndrome
- - radiation
- - oxygen toxicity
- edema fluid has high protein concentration
- 3. Decrease in interstitial hydrostatic pressure [Pi]
- (common cause of unilateral pulmonary edema)
- - rapid removal of pleural effusion or pneumothorax
- - rapid re-expansion of collapsed lung
- - hyperinflation of lung
- 4. Decrease colloid osmotic pressure [πc]
- - Saline oversaturation
- - Hypoproteinemia
- 5. Lymphoid insufficiency
- - silicosis (rare - from sand blasting)
- - lymphangitis carcinomatosa
- - lung transplantation (loss of lymphatics)
- 6. Uncertain etiology
- - high-altitude pulmonary edema (HAPE)
- 1. Strong association with high pulmonary artery pressure but normal wedge pressures
- 2. High permeability edema with high concentrations of large molecular weight proteins, cell
- (high protein concentration on lavage; thought to be due to uneven hypoxemic vasoconstriction, leading to high pressure in some capillaries --> rupture)
- - heroin, morphine
- - pneurogenic pulmonary edema
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Pulmonary Edema
Clinical presentation
- dyspnea, orthopnea, paroxysmal nocturnal dyspnea -- sx thought to be from stimulation of J (juxtacapillary) receptors on the vagus nerve
- cough, may be pink frothy sputum
- crepitations on auscultation
- radiograph: septal lines, blotchy shadowing
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Pulmonary Edema
Lung function
- Interstitial edema:
- - Generally has little effect
- - Some evidence that lung compliance is reduced
- - Perivascular and peribronchial cuffing may increase pulmonary vascular and airway resistance
Alveolar edema:
- 1. Mechanics
- - Lung compliance is reduced
- - Airway resistance is increased
- 2. Gas exchange
- - Hypoxemia due to shunt and ventilation-perfusion inequality
- - No CO2 retention
3. Pulmonary vascular resistance increased
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