The most common causes of pulmonary edema are related to problems with the heart, particularly heart abnormalities, heart failure, and heart attack, which is known medically as myocardial infarction. Artery blockage problems known as myocardial ischemia are often included on this list, too. The heart and lungs are connected in a number of important ways, and when the heart isn’t working properly it can impact how much blood is pumped in and out of the lungs — which, in turn, can cause or worsen fluid build-up problems. These aren’t the only potential causes of edema, though; lung injury and trauma are also high on the list. Blood issues, including pancreatitis and bad reactions to transfusions, are also possibilities, as are environmental factors like heavy air pollution or reduced oxygen levels, particularly at high altitudes. The condition is quite serious, but can usually be treated if care is sought promptly. Anyone who is experiencing difficulty breathing, is vomiting blood, or who experiences periodic bursts of intense difficulty breathing should usually get medical attention as soon as possible.
Understanding Edemas Generally
“Edema” is a medical term used to describe swelling that is caused by fluid build-up. Pulmonary edema is a condition where fluid accumulates within the lung tissue. This fluid is often blood, but it can also be water, lymphatic fluid, mucus, or a combination of some or all of these. The extent of the pulmonary edema depends on osmotic and hydrostatic forces within the pulmonary capillaries.
The primary cardiogenic, or heart-related, causes of pulmonary edema include a variety of heart abnormalities that result in an increase in the pulmonary venous pressure. This increase shifts the delicate balance between the interstitial tissue and the pulmonary capillaries. When this happens, the hydrostatic pressure elevates, promoting the collection of fluid into the capillaries and thereafter into the alveoli. Alveoli are tiny air sacs that easily fill with fluid, resulting in shortness of breath and coughing.
Heart Conditions and Failure
Heart conditions like congestive heart failure, artery blockages and collapse, heart attack, and valve abnormalities can also be causes. These problems often result in volume overloads of the left ventricle, which causes an imbalance when it comes to how much blood is pumped to the lungs and how well they are oxygenated .
When it comes to the heart valves specifically, some of the biggest causes of pulmonary edema include mitral valve stenosis, mitral valve regurgitation, and aortic insufficiency. Ventricular septal defects, which are holes within the cardiac muscle separating the two lower chambers of the heart, can also be problematic.
Lung Injury and Trauma
Direct injury to the lungs is also a very common cause. A lung that collapses is an extreme example, but even severe bruising or scarring can cause a collection of blood and lung fluids to pool. Edema increases inside the lungs from leakage of proteins through damaged capillary linings. Fluid follows the leaking proteins due to oncotic forces causing a dysfunction of the surfactant-lined alveoli.
Pulmonary edema also can result from lung re-expansion after a lung collapse. Some of the most common symptoms of injury-related edema include extreme bouts of shortness of breath, particularly when lying down, and a bluish pallor to the skin.
Some lung injuries causing pulmonary edema are due to elevated hydrostatic pressure. For example, high altitude pulmonary edema (HAPE) is an acute mountain illness that occurs when persons ascend to high elevations without proper acclimation. Of all the causes of this condition, HAPE has the simplest treatment: people usually need only to descend to lower altitudes to get things re-stabilized.
Injuries also can be caused by pulmonary contusion, pneumonia, pulmonary embolism and oxygen toxicity, which occurs from breathing high concentrations of oxygen at high atmospheric pressures. Air pollution can also be a cause, particularly in children and particularly in places where the air quality is generally bad to start with.
Problems Elsewhere in the Body
Hematogenous injuries causing pulmonary edema include an assortment of diseases. These are usually serious conditions and can include sepsis, disseminated intravascular coagulation (DIC), and pancreatitis. Multiple transfusions with negative reactions can also lead to fluid and swelling, as can trauma to other parts of the body that may seem unrelated. If the injury is bad enough, problems can travel through the blood to many different places. Extended time on cardiopulmonary bypass during surgeries can also sometimes lead to lung edema.
Elevations of hydrostatic pressure that can lead to swelling are commonly also caused by increased intracerebral pressure in the brain, which is called neurogenic pulmonary edema. Some chemical causes of pulmonary edema include radiographic contrast allergies, salicylate intoxication and inhaled toxins, such as occurs in smoke inhalation.