What is this Condition?
In pulmonary edema, fluid builds up in the spaces outside the lung’s blood vessels (called extravascular spaces). In one form of this disorder, cardiogenic pulmonary edema, this accumulation is caused by rising pressure in the respiratory veins and tiny blood vessels called capillaries. A common complication of heart disorders, pulmonary edema can become a chronic condition, or it can develop quickly and rapidly become fatal.
What Causes it?
Pulmonary edema usually is caused by failure of the left ventricle, the heart’s main chamber, due to various types of heart disease. In these diseases, the damaged left ventricle requires increased filling pressures to pump enough blood to all the parts of the body. The increased pressures are transmitted to the heart’s other chambers and to veins and capillaries in the lungs. Eventually, fluid in the blood vessels enters the spaces between the tissues of the lungs. This makes it harder for the lungs to expand and impedes the exchange of air and gases between the lungs and blood moving through lung capillaries.
Besides heart disease, other conditions that can predispose a person to pulmonary edema include:
o excessive amounts of intravenous fluids
o certain kidney diseases, extensive burns, liver disease, and nutritional deficiencies
o impaired lymphatic drainage of the lungs, as occurs in Hodgkin’s disease
o impaired emptying of the heart’s left upper chamber, as occurs in narrowing of the heart’s mitral valve
o conditions that cause blockage of the respiratory veins.
What are its Symptoms?
Early symptoms of pulmonary edema reflect poor lung expansion and extravascular fluid buildup. They include:
o shortness of breath on exertion
o sudden attacks of respiratory distress after several hours of sleep
o difficulty breathing except when in an upright position
On examination, the doctor may discover a rapid pulse, rapid breathing, an abnormal breath sound called crackles, an enlarged neck vein, and abnormal heart sounds.
With severe pulmonary edema, early symptoms may worsen as air sacs in the lungs and small respiratory airways fill with fluid. Breathing becomes labored and rapid, and coughing produces frothy, bloody sputum. The pulse quickens and the heart rhythm may become disturbed. The skin is cold, clammy, sweaty, and bluish. As the heart pumps less and less blood, the blood pressure drops and the pulse becomes thready.
How is it Diagnosed?
The doctor makes a working diagnosis based on the persons symptoms and physical exam results and orders measurements of arterial blood gases, which usually show decreased oxygen with a variable carbon dioxide level. These measurements may also reveal a metabolic disturbance, such as respiratory alkalosis, respiratory acidosis, or metabolic acidosis. Chest X-rays typically reveal diffuse haziness in the lungs and, often, an enlarged heart and abnormal fluid buildup in the lungs.
The person may undergo a diagnostic procedure called pulmonary artery catheterization to help confirm failure of the left ventricle and rule out adult respiratory distress syndrome, which causes similar symptoms.
How is it Treated?
Treatment of pulmonary edema aims to reduce the amount of extravascular lung fluid, to improve gas exchange and heart function and, if possible, to correct underlying disease.
Usually, the person receives high concentrations of oxygen. If an acceptable arterial blood oxygen level still can’t be maintained, the person receives mechanical ventilation to improve oxygen delivery to the tissues and to treat acid-base disturbances.
The individual also may receive diuretics (for example, Lasix) to promote fluid elimination through urination, which in turn helps to reduce extravascular fluid.
To treat heart dysfunction, the person may receive a digitalis glycoside or other drugs that improve heart contraction. Some people also receive drugs that dilate the arteries such as Nipride. Morphine may be given to reduce anxiety, ease breathing, and improve blood flow from the pulmonary circulation to the arms and legs.