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Pulmonary changes at high altitude and altitude sickness
Congenital pulmonary airway malformation
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Meconium aspiration syndrome
Neonatal respiratory distress syndrome
Sudden infant death syndrome
Transient tachypnea of the newborn
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Apnea, hypoventilation and pulmonary hypertension: Pathology review
Cystic fibrosis: Pathology review
Deep vein thrombosis and pulmonary embolism: Pathology review
Lung cancer and mesothelioma: Pathology review
Obstructive lung diseases: Pathology review
Pleural effusion, pneumothorax, hemothorax and atelectasis: Pathology review
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Respiratory distress syndrome: Pathology review
Restrictive lung diseases: Pathology review
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opiod analgesics p. 569
compliance in p. 685
consolidation in p. 300
heart failure p. 316
loop diuretics for p. 628
LV failure p. 314
mannitol p. 627
nitrates for p. 323
opioids for p. 569
preeclampsia and p. 662
renal failure p. 623
transfusion-related injury p. 112
Pulmonary edema refers to the buildup of fluid in the lungs including the airways like the alveoli - which are the tiny air sacs - as well as in the interstitium, which is the lung tissue that’s sandwiched between the alveoli and the capillaries.
This space is mostly full of proteins, and when it starts filling up with fluid, it can make it hard for oxygen to cross over from the alveoli into the capillary, leaving the body hypoxic - or deprived of oxygen.
To understand pulmonary edema, let’s first talk about the three main factors that determine how fluid moves between the capillaries and interstitial fluid, which are the hydrostatic pressure, oncotic pressure and capillary permeability.
Hydrostatic pressure refers to the pressure felt by fluid in a confined space, pushing the fluid out of that space.
In the interstitial space, it’s the same thing as the blood pressure in the pulmonary capillaries, and because the pulmonary circulation is a low pressure system, the hydrostatic pressure is pretty low. But it’s still higher than the hydrostatic pressure exerted by the interstitial fluid of the lungs - which is almost zero.
So, to be clear, if hydrostatic pressure was the only factor involved, a lot of fluid would be continuously leaking out of the pulmonary capillaries into the lung’s interstitial space.
The next factor, though, is oncotic pressure; which is a type of osmotic pressure exerted by cells and proteins that can’t cross the capillary membrane and therefore tend to attract fluid.
The oncotic pressure is higher in the pulmonary capillaries than in the interstitial fluid, so it opposes the hydrostatic pressure.
Pulmonary edema is a condition in which fluid accumulates in the lungs, making it difficult for oxygen to pass through the alveoli and into the bloodstream. It is often due to the left ventricular heart failure to adequately remove blood from the pulmonary circulation, which is known as cardiogenic pulmonary edema. It can also be due to an injury to the lung parenchyma or vasculature of the lung - known as noncardiogenic pulmonary edema.
If not treated, pulmonary edema can lead to respiratory failure or cardiac arrest due to hypoxia. Treatment focuses on improving respiratory function, treating the underlying cause, and preventing and avoiding further damage to the lung.
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