What is a pulmonary edema?

Quick Answer
A lung ailment in which the pressure in the blood vessels in the lungs exceeds the pressure in the air sacs, resulting in fluid being pushed from the blood into the lungs. This makes it difficult to transfer gases between the blood and lungs.
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Causes and Symptoms

There are two major causes of pulmonary edema. The most common is when the heart or circulatory system is not functioning properly. The other is when there is direct injury to the lungs, which can be caused by toxic gases, trauma, or severe infection.

When the heart muscle becomes damaged, often by a heart attack, the muscle in the left ventricle cannot pump blood as well as that in the right ventricle. This causes the blood pressure in the pulmonary veins of the lungs to rise. When the blood pressure becomes higher than the air pressure in the alveoli, fluid from the blood crosses the membranes and goes into the lungs. The fluid in the lungs makes it difficult for oxygen to move from the alveoli into the blood, resulting in shortness of breath.

Another heart condition that can cause pulmonary edema is a heart valve malfunction. The problem begins when the mitral valve, between the left atrium and left ventricle, becomes narrowed or allows some blood to flow backward. In either case, the movement of blood from the atrium to the ventricle is compromised, causing blood to back up into the pulmonary system and triggering high blood pressure. High pulmonary vein pressure can also be due to cardiomyopathy, in which the heart muscle becomes thick, enlarged, or rigid. When this happens, the heart muscle does not contract well, and, as with the other causes of pulmonary edema, the pressure in the veins gets too high.

Breathing toxic gases can irritate the lining of the lungs, resulting in fluid release in the alveoli. Blunt forces to the chest can damage capillaries in the lungs. Lung infections can cause an inflammatory response. All these conditions result in fluid collecting in the alveoli, making it difficult for oxygen to move into the blood and causing shortness of breath.

The major symptom of pulmonary edema is difficulty breathing. The patient may cough up blood or a pink, frothy fluid. Sometimes, rapid breathing, dizziness, or general weakness is observed. These symptoms are the result of the body’s tissues not receiving enough oxygen. If pulmonary edema is left untreated, the patient can enter into a coma and even die. If the condition develops slowly, it can be accompanied by ankle edema, breathlessness when lying down, and waking in the middle of the night with shortness of breath.

Treatment and Therapy

The initial treatment for severe pulmonary edema is to administer high-flow oxygen to increase the amount of oxygen getting into the blood. Other treatments depend on the origin of the condition. If the cause is cardiovascular, then diuretics can be given to decrease the total fluid levels in the body. This will help to decrease the blood pressure, including in the pulmonary veins, resulting in less fluid moving from the blood to the lungs. When the cause is infection, antibiotics are administered. Destroying the bacteria will take away the inflammation and the fluid from the lungs. In cases of toxic gas inhalation, the person must first be removed from exposure to the gas. Often, an inhaler is used to dilate the bronchioles in the lungs in order to increase airflow. In all these cases, the most important objective is to get sufficient oxygen from the lungs into the blood.

Perspectives and Prospects

The recorded history of heart failure dates back to ancient Greece, where it was reported that fluid could be heard in the lungs when placing the ear against a patient’s chest. Due to the lack of information about the cause of the fluid, it is difficult to know the full context of the ancient medical writings. A better understanding was developed in the seventeenth century, when William Harvey described how the blood circulates throughout the body. In the late nineteenth century, the development of the electrocardiogram by Willem Einthoven and x-ray technology by Wilhelm Conrad Röntgen led to an even better understanding.

Treatments for congestive heart failure have varied throughout history. For centuries and into the eighteenth century, bloodletting and leeches were used to reduce fluid volumes in the body. In the late eighteenth century, William Withering discovered that digitalis led to significant improvements in patients with congestive heart failure. Digitalis is still used today to treat various heart conditions. The next treatment to reduce the fluid in the body was developed in the late nineteenth century by Reginald Southey, who used tubes to drain fluid from the ankles and feet. By the twentieth century, diuretics had been developed that are still used today.


American Medical Association. American Medical Association Family Medical Guide. 4th ed. Hoboken, N.J.: John Wiley & Sons, 2004.

Dugdale, David C., III, Michael A. Chen, and David Zieve. “Pulmonary Edema.” MedlinePlus, June 4, 2012.

Goldmann, David R., ed. American College of Physicians Complete Home Medical Guide. 2d ed. New York: DK Publishing, 2003.

Litin, Scott C., ed. Mayo Clinic Family Health Book. 4th ed. Chicago: Time Inc. Home Entertainment, 2009.

“Pulmonary Edema.” Mayo Clinic, July 29, 2011.

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