Symptoms and Causes of Pulmonary Edema

Pulmonary edema, sometimes called "wet lung," is a serious medical condition in which the air sacs of the lung (alveoli) fill with fluid, making breathing difficult. Symptoms include shortness of breath, wheezing, coughing, and a frothy discharge.

Pulmonary edema is a very serious condition associated with heart disease but one that can occur due to non-heart-related causes. In people with a terminal illness, the condition is often fatal. In others, pulmonary edema is treatable, with as many people surviving for several years or more.

This article discusses the causes and symptoms of pulmonary edema, including how this lung complication is diagnosed and treated. It also discusses survival rates, life expectancy statistics, and ways to reduce your risk.

What Is Pulmonary Edema?

"Pulmonary" is the medical term for the respiratory tract, while "edema" is swelling caused by excess fluid trapped in the body's tissues. With pulmonary edema, alveoli at the very end of the branches of the airways are the tissues that are subject to fluid accumulation.

Under normal circumstances, alveoli are where oxygen and carbon dioxide are exchanged as you inhale and exhale. As you inhale, oxygen molecules move from the alveoli to red blood cells, which carry the molecules to tissues of the body. The cells then carry carbon dioxide (a waste product of cellular metabolism) back to the alveoli to be expelled from the body as you exhale.

With pulmonary edema, this process is interrupted, and you can neither deliver enough oxygen to the blood nor remove enough carbon dioxide from the blood.

Symptoms of Pulmonary Edema

The symptoms of pulmonary edema can vary based on the underlying cause. The causes may be categorized as being either acute (suddenly and severe) or chronic (persistent or recurring).

Acute pulmonary edema signs and symptoms include:

• Shortness of breath (dyspnea)
• Wheezing
• Rapid, shallow breath (tachypnea)
• Coughing up a pink, frothy sputum (hemoptysis)
• Difficulty breathing when lying down (orthopnea)
• Crackling sounds in the lungs (rales)
  
• Heart palpitations or murmurs
• Excessive sweating
• Pale skin (pallor)
• Anxiety or restlessness
  

Chronic pulmonary edema signs and symptoms include:

• A new or worsening cough
• Persistent fatigue
• Difficulty breathing when lying flat (that improves when sitting up)
• Difficulty breathing and shortness of breath with physical activity
  
• Waking up from sleep with a drowning feeling (paroxysmal nocturnal dyspnea)
• Rapid, unexplained weight gain
• Feet and ankle swelling (peripheral edema)
  

Complications

The lung is interconnected with the heart, kidneys, and liver, and the disruption of one of these systems can affect the others.

With pulmonary edema, the pressure placed on the pulmonary artery can lead to pulmonary hypertension (high blood pressure in the lungs). This can cause adverse effects in the associated organs.

In severe cases, this can lead to complications like:

• Heart failure: The inability of the heart to pump enough blood to service the body's needs
• Hepatomegaly; An enlarged liver
• Pleural effusion: A buildup of fluid in the membranes surrounding the lungs
• Ascites: Fluid accumulation in the abdomen caused by liver congestion
  

What Causes Pulmonary Edema?

Pulmonary edema is broadly characterized as either cardiac pulmonary edema (involving the cardiovascular system) or non-cardiac pulmonary edema (not involving the cardiovascular system). Both are more common in older adults and people with chronic diseases.

Cardiac Pulmonary Edema

Cardiac pulmonary edema (or cardiogenic pulmonary edema) is the most common form of the disease. It occurs when a heart condition increases blood pressure within the heart. The pressure is then transferred to the lungs' capillaries, causing fluid to leak into the airways and accumulate in the alveoli.

Almost any kind of heart disease can lead to pulmonary edema. The most common causes include:

• Cardiac arrhythmia: Abnormal heart rhythms
• Cardiomyopathy; Heart muscle damage
• Congestive heart failure: The inability of the heart to pump blood efficiently
• Coronary artery disease: Caused by the buildup of plaque on artery walls
• Heart valve diseases: Dysfunction of the valves that direct blood flow
• Hypertension: High blood pressure
• Hypertensive kidney disease: High blood pressure caused by renal artery stenosis
• Myocarditis: Inflammation of the heart muscle

Non-Cardiac Pulmonary Edema

Non-cardiac pulmonary edema (or noncardiogenic pulmonary edema), occurs when capillaries in the lungs become damaged for reasons unrelated to the heart.

The damage may be caused by drastic changes in airway pressure, by the dysfunction of the airways, or by agents that directly damage airway tissues. When this happens, fluids can leak into the alveoli, causing edema.

Noncardiogenic causes of pulmonary edema include:

• Acute respiratory distress syndrome (ARDS): A potentially fatal form of respiratory failure
  
• Drug side effects or overdose: Including chemotherapy, street drugs like heroin, and heart medications like amiodarone
• High-altitude pulmonary edema (HAPE): A severe manifestation of high-altitude illness
  
• Inhaled toxins: Including smoke, chlorine, or ammonia
  
• Near-drowning: Results in disruption of alveolar tissues and makes them more porous
• Negative pressure pulmonary edema: A blocked upper airway, often the result of intubation and general anesthesia
• Neurogenic pulmonary edema (NPE): Including neurological problems like stroke, traumatic brain injury, or multiple sclerosis
• Pulmonary embolism: A blood clot in the lungs
• Transfusion-related lung injury: Caused when transfused blood overloads the heart muscle, placing pressure on the lungs
• Tropical viral illnesses: Including hantavirus and dengue virus
  

How Is Pulmonary Edema Diagnosed?

Rapidly diagnosing pulmonary edema is critical, especially if the symptoms are sudden and severe. The diagnosis will start with a physical exam (including listening to lung sounds with a stethoscope and taking your blood pressure) and be accompanied by a review of your medical history and family history.

Other tests may include:

• Arterial blood gas (ABG): A blood test that measures the composition of gas in your blood
• B-type natriuretic peptide (BNP): A blood test used to diagnose heart failure
• Pulse oximetry: A non-invasive device that measures blood oxygen levels
• Chest X-ray: A plain film imaging study created with ionizing radiation
  
• Computed tomography (CT) scan: A technology that composites multiple X-ray images
• Ultrasound: A non-invasive imaging tool that creates images with reflected sound waves
• Electrocardiogram (ECG): A test that measures the electrical activity of your heart
• Echocardiogram: A form of ultrasound that examines the heart muscle
• Cardiac catheterization and coronary angiogram: A procedure that can detect heart blockages by threading a narrow tube (catheter) to your heart through a vein in your groin

How Is Pulmonary Edema Treated?

The immediate treatment goals for pulmonary edema are to reduce the fluid buildup in the lungs and restore blood oxygen levels to normal. The ultimate treatment, though, is to resolve the underlying cause.

The treatment may involve:

• Oxygen therapy: Delivered via a mask or a tube (called a cannula) beneath your nose
• Mechanical ventilation: Involves intubation and connection to a machine that breathes for you
• Diuretics: Also known as "water pills," which reduce blood pressure by promoting urination
• Nitroglycerin: A drug that can quickly increase heart output in people with heart failure
• Inotropes: A class of drugs that can improve heart function in people with heart failure
• Morphine: Used in severe cases to rapidly decrease capillary pressure
  

Outlook for Pulmonary Edema

The prognosis (outlook) for people with pulmonary edema depends on several factors, including the underlying cause and how quickly the condition is diagnosed and treated.

In about one-quarter of hospitalized people, cardiogenic pulmonary edema is fatal. While roughly half will live for at least another year, only around 15% live longer than six years.

The outlook for people with noncardiogenic pulmonary edema is generally better, with 43% living for at least four years and some living many years more.

Pulmonary edema from ARDS is also often fatal. In severe cases, up to 60% of people die in the hospital. Those who survive often diminished functional capacity and mental health problems which can severely decrease their quality of life. 

In critically ill patients, neurogenic pulmonary edema is almost always fatal, primarily when it is associated with stroke. Approximately 40% will survive NPE, and the outlook can improve significantly after 48 to 72 hours of aggressive treatment. 

How to Prevent Pulmonary Edema

Given that pulmonary edema has many causes, there is not always a way to prevent this potentially life-threatening condition.

But given that heart disease is the most likely cause, you would be well served to take the following steps to reduce your risk of heart disease:

1. Eat a healthy, balanced diet with whole grains, fruits, vegetables, healthy fats, and fish.
2. Be physically active with regular aerobic exercise and strength training.
3. Maintain a healthy weight, losing weight if necessary.
4. Give up smoking. Ask your healthcare provider to prescribe smoking cessation tools if needed.
5. Reduce your alcohol intake. If you have a drinking problem, seek professional help.
6. Keep your blood pressure under control as directed by your healthcare provider.
7. Keep your diabetes under control with diet, exercise, and medications if needed.

If you are prescribed heart medications, take them as prescribed without interruption and see your primary care provider or cardiologist for regular checkups and medication refills.

Summary

Pulmonary edema is a potentially fatal medical condition where excess fluid fills the lungs' alveoli. It is most commonly caused by heart disease but can also be caused by various non-cardiac causes like stroke or ARDS. Symptoms include rapid and shallow breathing, difficulty breathing while lying down, a crackling sound in the lungs, wheezing, and frothy or pink lung secretions.

Blood tests, imaging studies, and cardiac catheterization may be used to confirm the diagnosis and narrow the possible causes. Treatments include oxygen therapy and medications that improve heart output and reduce pressure in lung capillaries.