Pulmonary edema is a condition caused by too much fluid in the lungs. This fluid collects in the many air sacs in the lungs, making it difficult to breathe.

In most cases, heart problems cause pulmonary edema. But fluid can collect in the lungs for other reasons. These include pneumonia, contact with certain toxins, medications, trauma to the chest wall, and traveling to or exercising at high elevations.

Pulmonary edema that develops suddenly (acute pulmonary edema) is a medical emergency that needs immediate care. Pulmonary edema can sometimes cause death. Prompt treatment might help. Treatment for pulmonary edema depends on the cause but generally includes additional oxygen and medications.


Pulmonary edema symptoms may appear suddenly or develop over time. Symptoms depend on the type of pulmonary edema.

Sudden (acute) pulmonary edema symptoms

  • Difficulty breathing (dyspnea) or extreme shortness of breath that worsens with activity or when lying down
  • A feeling of suffocating or drowning that worsens when lying down
  • A cough that produces frothy sputum that may have blood in it
  • A rapid, irregular heartbeat (palpitations)
  • Anxiety, restlessness or a feeling that something bad is about to happen
  • Cold, clammy skin
  • Wheezing or gasping for breath

Long-term (chronic) pulmonary edema signs and symptoms

  • Awakening at night with a cough or breathless feeling that may be relieved by sitting up
  • Difficulty breathing with activity or when lying flat
  • Fatigue
  • More shortness of breath than usual when you're physically active
  • New or worsening cough
  • Rapid weight gain
  • Swelling in the legs and feet
  • Wheezing

High-altitude pulmonary edema (HAPE) signs and symptoms

high-altitude pulmonary edema (HAPE) can occur in adults and children who travel to or exercise at high altitudes. Symptoms are similar to those that occur with acute pulmonary edema and can include:

  • Headache, which may be the first symptom
  • Shortness of breath with activity, which becomes shortness of breath at rest
  • Not being able to exercise as much as you once could
  • Dry cough, at first
  • Later, a cough that produces frothy sputum that may look pink or have blood in it
  • A very fast heartbeat (tachycardia)
  • Weakness
  • Chest pain
  • Low fever

Symptoms of high-altitude pulmonary edema (HAPE) tend to get worse at night.

When to see a doctor

Pulmonary edema that comes on suddenly (acute pulmonary edema) is life-threatening. Call 911 or emergency medical help if you have any of the following acute symptoms:

  • Shortness of breath, especially if it comes on suddenly
  • Trouble breathing or a feeling of suffocating (dyspnea)
  • A bubbly, wheezing or gasping sound when breathing
  • Coughing up phlegm that looks pink or has blood in it
  • Breathing difficulty with a lot of sweating
  • A blue or gray color to the skin
  • Confusion
  • A big drop in blood pressure that causes lightheadedness, dizziness, weakness or sweating
  • A sudden worsening of any of pulmonary edema symptoms

Don't drive yourself to the hospital. Instead, call 911 or emergency medical care and wait for help.


The causes of pulmonary edema vary. Pulmonary edema falls into two categories, depending on where the problem starts.

  • If a heart problem causes the pulmonary edema, it's called cardiogenic pulmonary edema. Most often, the fluid buildup in the lungs is due to a heart condition.
  • If pulmonary edema is not heart related, it's called noncardiogenic pulmonary edema.
  • Sometimes, pulmonary edema can be caused by both a heart problem and a nonheart problem.

Understanding the relationship between the lungs and the heart can help explain why pulmonary edema may occur.

How the lungs work

Lungs contain many small, elastic air sacs called alveoli. With each breath, these air sacs take in oxygen and release carbon dioxide. Typically, this exchange of gases occurs without problems.

But sometimes, the alveoli fill with fluid instead of air. This keeps the bloodstream from taking in oxygen.

How the heart works

The typical heart is made of two upper and two lower chambers. The upper chambers (the right and left atria) receive incoming blood and pump it into the lower chambers (right and left ventricles). The lower chambers pump blood out of the heart.

Typically, blood without oxygen from all over the body enters the right atrium then the right ventricle. From there it's pumped through large blood vessels (pulmonary arteries) to the lungs. There, the blood releases carbon dioxide and picks up oxygen as it flows by the alveoli.

The oxygen-rich blood then returns to the left atrium through the pulmonary veins. It then flows through the mitral valve into the left ventricle. Finally, it leaves the heart through the body's main artery (aorta).

The heart valves keep blood flowing in the right direction. The aortic valve keeps the blood from flowing backward into the heart. From the aorta, the blood travels to the rest of the body.

Chambers and valves of the heart

Chambers and valves of the heart

A typical heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of the heart. The heart valves, which keep blood flowing in the right direction, are gates at the chamber openings.

Heart-related (cardiogenic) pulmonary edema

Cardiogenic pulmonary edema is caused by increased pressures in the heart.

It's usually a result of heart failure. When a diseased or overworked left lower heart chamber (left ventricle) can't pump out enough of the blood it gets from the lungs, pressures in the heart go up. The increased pressure pushes fluid through the blood vessel walls into the air sacs.

Medical conditions that can cause heart failure and lead to pulmonary edema include:

  • Coronary artery disease. Over time, the arteries that supply blood to the heart muscle can become narrow from fatty deposits (plaques). A slow narrowing of the coronary arteries can weaken the left ventricle.

    Sometimes, a blood clot forms in one of these narrowed arteries. The clot blocks blood flow and damages part of the heart muscle, resulting in a heart attack. A damaged heart muscle can no longer pump as well as it should.

  • Cardiomyopathy. This term means heart muscle damage. With cardiomyopathy, the heart must pump harder, and pressures rise. Then the heart might not be able to work harder when needed, such as during exercise or with an infection or a rise in blood pressure. When the left ventricle can't keep up with the demands that are placed on it, fluid backs up into the lungs.
  • Heart valve problems. Narrowing (stenosis) of the aortic or mitral heart valves or a valve that leaks or doesn't close properly affects blood flow into the heart. A valve leak that develops suddenly might cause sudden and severe pulmonary edema.
  • High blood pressure (hypertension). Untreated or uncontrolled high blood pressure can enlarge the heart.
  • Other heart problems. Inflammation of the heart muscle (myocarditis), heart problems present at birth (congenital heart defects) and irregular heart rhythms (arrhythmias) also may cause pulmonary edema.
  • Kidney disease. High blood pressure due to narrowed kidney arteries (renal artery stenosis) or fluid buildup due to kidney disease can cause pulmonary edema.
  • Chronic health conditions. Thyroid disease and a buildup of iron (hemochromatosis) or protein (amyloidosis) also may contribute to heart failure and cause pulmonary edema.

Non-heart-related (noncardiogenic) pulmonary edema

Pulmonary edema that is not caused by increased pressures in the heart is called noncardiogenic pulmonary edema.

Causes of noncardiogenic pulmonary edema include:

  • Acute respiratory distress syndrome (ARDS). This serious disorder occurs when the lungs suddenly fill with fluid. Many conditions can cause acute respiratory distress syndrome (ARDS), including severe injury (trauma), widespread infection (sepsis), pneumonia and severe bleeding.
  • Drug reaction or drug overdose. Many drugs — ranging from aspirin to illegal drugs such as heroin and cocaine — are known to cause pulmonary edema.
  • Blood clot in the lungs (pulmonary embolism). A blood clot moving from the blood vessels in the legs to the lungs can cause pulmonary edema.
  • Exposure to certain toxins. Inhaling toxins or breathing in some stomach contents when vomiting (aspiration) causes intense irritation of the small airways and air sacs, resulting in fluid buildup.
  • High altitudes. Pulmonary edema has been seen in mountain climbers, skiers, hikers and other people who travel to high elevations, usually above 8,000 feet (about 2,400 meters). High-altitude pulmonary edema (HAPE) generally occurs in those who don't take the days or weeks needed to become used to the elevation. But people who live at high altitudes can get HAPE with no elevation change if they have a respiratory illness.
  • Near drowning. Inhaling water causes fluid buildup in the lungs.
  • Negative pressure pulmonary edema. A blocked upper airway causes negative pressure in the lungs from trying to breathe through the blockage. With treatment, most people with this type of pulmonary edema recover in about 24 hours.
  • Nervous system conditions or surgeries. A type of pulmonary edema called neurogenic pulmonary edema can occur after a head injury, seizure or brain surgery.
  • Smoke inhalation. Smoke from a fire contains chemicals that damage the membrane between the air sacs and the capillaries. The damage allows fluid to enter the lungs.
  • Transfusion-related lung injury. Blood transfusions may cause fluid overload in the left ventricle, leading to pulmonary edema.
  • Viral illnesses. Viruses such as the hantavirus and dengue virus can cause pulmonary edema.
High-altitude pulmonary edema

High-altitude pulmonary edema

Air sacs in the lungs, called alveoli, take in oxygen and release carbon dioxide. In high-altitude pulmonary edema (HAPE), it's believed that blood vessels in the lungs squeeze together (constrict), increasing pressure. This causes fluid to leak from the blood vessels to the lung tissues and eventually into the air sacs.

Risk factors

Heart failure and other heart conditions that raise pressure in the heart increase the risk of pulmonary edema. Risk factors for heart failure include:

  • Irregular heart rhythms (arrhythmias)
  • Alcohol use
  • Congenital heart disease
  • Coronary artery disease
  • Diabetes
  • Heart valve disease
  • High blood pressure
  • Sleep apnea

Some nervous system conditions and lung damage due to near drowning, drug use, inhaling smoke, viral illnesses and blood clots also raise the risk.

People who travel to high-altitude locations above 8,000 feet (about 2,400 meters) are more likely to develop high-altitude pulmonary edema (HAPE). It usually affects those who don't take the time — a few days to a week or more — to get used to the elevation.

Children who already have pulmonary hypertension and structural heart defects may be more likely to get HAPE.


Complications of pulmonary edema depend on the cause.

In general, if pulmonary edema continues, the pressure in the pulmonary artery can rise (pulmonary hypertension). Eventually, the heart becomes weak and begins to fail, and pressures in the heart and lungs go up.

Pulmonary edema complications may include:

  • Breathing difficulty
  • Swelling of the legs, feet and belly area
  • Buildup of fluid in the membranes that surround the lungs (pleural effusion)
  • Congestion and swelling of the liver

Immediate treatment is necessary for acute pulmonary edema to prevent death.


You may be able to prevent pulmonary edema by managing existing heart or lung conditions and following a healthy lifestyle.

For example, controlling cholesterol and blood pressure can help lower the risk of heart disease. Follow these tips to keep your heart healthy:

  • Eat a healthy diet rich in fresh fruits, vegetables, whole grains, fat-free or low-fat dairy, and a variety of proteins.
  • Don't smoke.
  • Get regular exercise.
  • Limit salt and alcohol.
  • Manage stress.
  • Manage weight.

Preventing high-altitude pulmonary edema (HAPE)

To prevent HAPE, gradually ascend to high elevations. Although recommendations vary, most experts advise increasing elevation no more than 1,000 to 1,200 feet (about 300 to 360 meters) a day once you reach 8,200 feet (about 2,500 meters).

Some climbers take prescription medications such as acetazolamide or nifedipine (Procardia) to help prevent symptoms of HAPE. To prevent HAPE, start taking the medication at least one day before ascent. Ask your health care provider how long you need to take the medication after you've arrived at your high-altitude destination.

May 27, 2022

  1. Mason RJ, et al. Pulmonary edema. In: Murray and Nadel's Textbook of Respiratory Medicine. 6th ed. Saunders Elsevier; 2016. https://www.clinicalkey.com. Accessed April 2, 2022.
  2. Pinto DS, et al. Pathophysiology of cardiogenic pulmonary edema. https://www.uptodate.com/contents/search. Accessed April 2, 2022.
  3. Ferri FF. Pulmonary edema. In: Ferri's Clinical Advisor 2022. Elsevier; 2022. https://www.clinicalkey.com. Accessed April 2, 2022.
  4. Givertz MM. Noncardiogenic pulmonary edema. https://www.uptodate.com/contents/search. Accessed April 2, 2022.
  5. Wemple M, et al. Neurogenic pulmonary edema. https://www.uptodate.com/contents/search. Accessed April 2, 2022.
  6. What is heart failure? National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health-topics/heart-failure. Accessed Sept. 11, 2020.
  7. Pulmonary edema. Merck Manual Professional Version. https://www.merckmanuals.com/professional/cardiovascular-disorders/heart-failure/pulmonary-edema. Accessed April 2, 2022.
  8. Tintinalli JE, et al., eds. High altitude disorders. In: Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 9th ed. McGraw Hill; 2020. http://accessmedicine.mhmedical.com. Accessed Sept. 11, 2020.
  9. Din-Lovinescu C, et al. Systematic review of negative pressure pulmonary edema in otolaryngology procedures. The Annals of Otology, Rhinology, and Laryngology. 2020; doi:10.1177/0003489420938817.
  10. Giesenhagen AM, et al. High altitude pulmonary edema in children: A single referral center evaluation. Journal of Pediatrics. 2019; doi:10.1016/j.jpeds.2019.02.028.
  11. What is ARDS? National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health-topics/ards. Accessed Sept. 11, 2020.
  12. What is the heart? National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health-topics/how-heart-works. Accessed Sept. 11, 2020.
  13. 2015-2020 Dietary Guidelines for Americans. U.S. Department of Health and Human Services and U.S. Department of Agriculture. https://health.gov/our-work/food-nutrition/2015-2020-dietary-guidelines/guidelines. Accessed Sept. 11, 2020.
  14. Pulse oximetry. American Lung Association. http://www.lung.org/lung-health-and-diseases/lung-procedures-and-tests/pulse-oximetry.html. Accessed Sept. 11, 2020.
  15. What is coronary heart disease? National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health-topics/coronary-heart-disease. Accessed Sept. 11, 2020.
  16. Loscalzo J, et al., eds. Cardiogenic shock and pulmonary edema. In: Harrison's Principles of Internal Medicine. 21st ed. McGraw-Hill; 2022. https://accessmedicine.mhmedical.com. Accessed April 4, 2022.
  17. Conde MV, et al. Overview of the management of postoperative pulmonary complications. https://www.uptodate.com/contents/search. Accessed April 2, 2022.
  18. Levitzky MG. Blood flow to the lung. In: Pulmonary Physiology. 9th ed. McGraw Hill; 2018. https://accessmedicine.mhmedical.com. Accessed Sept. 14, 2020.
  19. Olson EJ (expert opinion). Mayo Clinic. Sept. 15, 2020.
  20. Yancy CW, et al. 2017 ACC/AHA/HFSA focused update of the 2013 ACCF/AHA guideline for the management of heart failure. Circulation. 2017; doi:10.1161/CIR.0.


Your gift holds great power – donate today!

Make your tax-deductible gift and be a part of the cutting-edge research and care that's changing medicine.