Pulmonary edema occurs when the air sacs (alveoli) in your lungs fill with fluid. The fluid buildup makes it hard for the lungs to do their job, including getting oxygen from the air you breathe. This can make it hard to breathe. The most common cause of pulmonary edema is heart failure. When the heart doesn’t work properly, it can cause pressure to rise in the veins (blood vessels) of the lungs. As pressure builds, fluid leaks out of the congested veins. It fills the alveoli. The extra fluid prevents oxygen from moving through the lungs as it should. But heart failure isn’t the only cause of pulmonary edema. Damage to the lungs or kidney failure can also cause fluid to fill the lungs. And in some cases, living or exercising at high altitudes can lead to fluid buildup in the lungs.
More than 1 million patients are admitted each year with a diagnosis of pulmonary edema secondary to cardiac causes (heart failure). An estimated 190,000 patients are diagnosed with acute lung injury each year. About 1.5 to 3.5 cases/100,000 population are diagnosed with Acute respiratory distress syndrome (ARDS).
Types of Pulmonary Edema
There are two main types of pulmonary edema, based on what is causing the lungs to fill up with fluid. One is cardiogenic edema that results from increased pressures in the heart. The other is non-cardiogenic, which can be caused by a number of conditions that damage the lungs.
Heart-Related (Cardiogenic) Edema
Heart-related edema is caused by increased pressures in the heart. According to Penn State Milton S. Hershey Medical Center, congestive heart failure is a common cause of this type of pulmonary edema.
When you develop congestive heart failure, the left ventricle of your heart stops working properly, causing the kidneys to filter less fluid out of the circulation into the urine. This increases pressure in the capillaries (small blood vessels) of the lungs and causes excess fluid to be pushed into the air sacs of the lungs, the liver, and the legs.
The most common causes of congestive heart failure include:
- Coronary artery disease
- High blood pressure
- Previous heart attack
- Renal artery stenosis
- Kidney disease
Non-Cardiogenic Pulmonary Edema
In non-cardiogenic pulmonary edema, the lungs fill up with fluid because the capillaries become leaky causing fluid to collect in the alveoli (tiny air sacs in the lungs).
Some factors that can cause non-cardiogenic pulmonary edema include:
- Acute respiratory distress syndrome (ARDS)
- Adverse drug reaction
- Pulmonary embolism
- Smoke inhalation
- Inhalation of toxins like heroin
- Organ failure (heart, kidney, liver)
High-altitude pulmonary edema (HAPE)
Aside from medical conditions, hikers and mountain climbers are at risk for pulmonary edema that’s caused by rapid altitude ascent, generally above 8,000 feet.
HAPE may lead to shortness of breath, coughing, rapid heartbeat, and decreased oxygen levels as a result of pressure from constricted pulmonary capillaries. Other risk factors for HAPE include genetic susceptibility and having smaller lungs.
To prevent HAPE, it is recommended to make gradual ascensions to higher heights. Mayo Clinic recommends climbing no more than 1,000 to 1,200 feet a day after you reach 8,200 feet. Climbers may also take medications like acetazolamide or nifedipine the day before ascent to reduce blood pressure and prevent motion sickness.
Pulmonary Edema risk factors
Movement of fluid from blood vessels into air spaces occurs due to either:
- Increased pressure in pulmonary veins – mostly due to
- Heart failure.
- Reduced protein in the blood – usually due to liver or kidney disease, or
- Increased capillary permeability (leaky blood vessels).
Causes of Pulmonary Edema
Pulmonary edema is often caused by congestive heart failure. When the heart is not able to pump efficiently, blood can back up into the veins that take blood through the lungs.
As the pressure in these blood vessels increases, fluid is pushed into the air spaces (alveoli) in the lungs. This fluid reduces normal oxygen movement through the lungs. These two factors combine to cause shortness of breath.
Congestive heart failure that leads to pulmonary edema may be caused by:
- Heart attack, or any disease of the heart that weakens or stiffens the heart muscle (cardiomyopathy)
- Leaking or narrowed heart valves (mitral or aortic valves)
- Sudden, severe high blood pressure (hypertension)
Pulmonary edema may also be caused by:
- Certain medicines
- High altitude exposure
- Kidney failure
- Narrowed arteries that bring blood to the kidneys
- Lung damage caused by poisonous gas or severe infection
- Major injury
Signs and Symptoms
Symptoms may start suddenly and get worse quickly. They include:
- Extreme shortness of breath and trouble breathing
- Tightness and pain in the chest
- Wheezing, coughing
- Bluish nails and lips
- Pink, frothy mucus coming from nose and mouth
If pulmonary edema is related to congestive heart failure, symptoms may come on more slowly. You may notice shortness of breath when you are lying down, quick weight gain from retaining fluid, and fatigue.
If pulmonary edema continues, it can raise pressure in the pulmonary artery (pulmonary hypertension), and eventually the right ventricle in your heart becomes weak and begins to fail. The right ventricle has a much thinner wall of muscle than does the left side of your heart because it is under less pressure to pump blood into the lungs. The increased pressure backs up into the right atrium and then into various parts of your body, where it can cause:
- Lower extremity and abdominal swelling
- Buildup of fluid in the membranes that surround your lungs (pleural effusion)
- Congestion and swelling of the liver
Left untreated, acute pulmonary edema can be deadly. In some instances, it may be fatal even if you receive treatment.
Diagnosis and test
An examination by a doctor will include:
- Checking the rate and rhythm of your heartbeat (pulse).
- Checking your blood pressure.
- Checking how fast you are breathing.
- Listening with a stethoscope for abnormal noises in the lungs, indicating that abnormal fluid is present.
- Listening for heart murmurs, indicating a problem with the heart valves.
Possible tests include:
Blood tests, which are carried out to look for:
- Kidney function
- Levels of salts in the blood.
- Whether pulmonary oedema has been caused by a heart attack.
- A substance called natriuretic peptide, which tends to be raised in people with heart failure.
Monitoring blood oxygen levels, using pulse oximetry, which uses a sensor placed over a thin area of skin such as a fingertip.
Chest X-ray to look for signs of heart failure or any other problem in the lungs, such as pneumonia.
An ultrasound scan of the heart (an echocardiogram) to see if there are problems with the heart muscle (such as weakness, thickness, failure to relax properly, leaky or narrow heart valves, or fluid surrounding the heart).
A ‘heart tracing’ (electrocardiogram, or ECG) to look for signs of a heart attack or problems with the heart rhythm.
Treatment and medications
Treatment will depend on what caused your pulmonary edema. If high altitude caused your pulmonary edema, your symptoms may go away when you go to a lower altitude. You may also need any of the following:
Diuretics: This medicine is given to remove excess fluid from around your lungs and decrease your blood pressure. You may urinate more often when you take this medicine.
Heart medicine: These medicines may be given to make your heartbeat stronger or more regular, or to lower your blood pressure.
Vasodilators: Vasodilators may improve blood flow by making the blood vessels in your heart and lungs wider. This may decrease the pressure in your blood vessels and improve your symptoms.
Oxygen: This may help you breathe better and decrease the pressure in your lungs. You may get oxygen through a plastic mask or nasal cannula. A nasal cannula is a pair of short, thin tubes that are placed inside your nostrils.
Noninvasive positive-pressure ventilation (NPPV): This is a machine that helps your lungs fill with air through a mask or a mouthpiece, and helps you breathe better. If a mask is used, it may go over your nose and mouth, or just your nose. Extra oxygen may also be given to you through the machine.
Ventilator: This is a machine that can breathe for you if you cannot breathe well on your own. You may have an endotracheal (ET) tube in your mouth or nose. The ET tube is hooked to the ventilator. The ventilator can also give oxygen to you.
How to prevent pulmonary edema?
Some lifestyle changes can prevent pulmonary edema or help keep the condition in check. Keep your heart healthy by:
- Eating plenty of vegetables, fruits, and whole grains
- Eating less salt
- Getting regular exercise
- Quitting smoking
- Keeping a healthy weight
If you’re going somewhere at a higher elevation, try to get used to the altitude change slowly. Talk to your doctor about medications that might make you less likely to get high-altitude pulmonary edema.