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| | ====[[Pulmonary Oedema|Pulmonary oedema]]==== | | ====[[Pulmonary Oedema|Pulmonary oedema]]==== |
| − | * In the normal state, pulmonary alveoli are kept dry by three mechanisms:
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| − | *# Normal "push-pull" mechanism at capillary level.
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| − | *# Efficient lymphatic drainage by rhythmic pumping action near airways.
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| − | *# Integrity of the alveolar epithelial basement membrane is relatively impermeable.
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| − | *#* Unlike the capillary basement membrane, which is relatively permeable.
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| − |
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| − | =====Pathogenesis=====
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| − | # The pumping efficiency of the lymphatics is exceeded.
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| − | # Fluid accumulates in connective tissue adjacent to airways.
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| − | # The alveolar walls fill with fluid.
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| − | # The alveoli abruptly and severely fill with fluid.
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| − | #* Associated with the disintegration of alveolar epithelial junctional complexes.
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| − |
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| − |
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| − | =====Haemodynamic type=====
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| − | * Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
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| − | ** I.e. is due to elevated pulmonary venous pressure.
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| − | * Potentially reversible.
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| − | * Causes:
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| − | *# '''Cardiogenic'''
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| − | *#* Usually left ventricular failure.
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| − | *#* Also occurs with cardiac overload due to valvular disease.
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| − | *# '''Mechanical'''
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| − | *#* Large primary pulmonary tumours.
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| − | *#* Severe metastatic disease.
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| − | *#* Granulomatous infections may raise pulmonary venous pressure.
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| − | *# '''Neurogenic'''
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| − | *#* Seizures or CNS disorder.
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| − | *#* Rare in domestic species.
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| − |
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| − | =====Permeability type=====
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| − | * Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
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| − | * Irreversible.
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| − | * Causes:
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| − | *# '''Toxins'''
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| − | *#* Bacterial
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| − | *#** [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas'']]
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| − | *#** [[:Category:Pasteurella and Mannheimia species|''Pasteurella'']]
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| − | *#** [[:Category:Staphylococcus species|''Staphylococcus'']]
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| − | *#* Chemical
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| − | *#** Paraquat.
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| − | *# '''Aspiration/inhalation'''
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| − | *#* Gastric contents (low pH)
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| − | *#* Smoke.
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| − | *#* Excess ozone.
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| − | *#* Oxygen.
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| − |
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| − | * There may be a combination of haemodynamic and permeability types in electrocution syndromes and "shock" lung.
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| − | ** E.g. in Adult Respiratory Distress Syndrome (ARDS).
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| − |
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| − |
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| − | [[Category:Circulatory Disorders - Pathology]]
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| − |
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| − |
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| | ==[[General Oedema|General oedema]]== | | ==[[General Oedema|General oedema]]== |