What Is Pulmonary Edema? What Causes Pulmonary Edema?

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Main Category: Respiratory / Asthma
Also Included In: Cardiovascular / Cardiology;  Heart Disease
Article Date: 15 Oct 2009 - 8:00 PDT

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Pulmonary edema (UK/Ireland: oedema) is fluid accumulation in the lungs. This fluid collects in air sacs in the lungs, making it difficult to breathe. It leads to impaired gas exchange and may cause respiratory failure.

According to Medilexicon's medical dictionary, pulmonary edema is: "edema of lungs usually resulting from mitral stenosis or left ventricular failure."

In most cases, heart problems cause pulmonary edema. But fluid can accumulate for other reasons, including pneumonia, exposure to certain toxins and medications, and exercising or living at high elevations.

Treatment depends on the cause, but it focuses on maximizing respiratory function and removing the source of the problem. It generally includes supplemental oxygen and medications.

When pulmonary edema develops suddenly, it is a medical emergency requiring immediate care. Pulmonary edema can sometimes be fatal. The outlook depends on the rapidity in receiving treatment along with treatment for the underlying problem.

What are the signs and symptoms of pulmonary edema?

A symptom is something the patient feels or reports, while a sign is something other people, including a doctor, may detect. For example, a headache may be a symptom, while a rash may be a sign.

Pulmonary edema symptoms may appear suddenly or develop gradually, depending on the cause.

Signs and symptoms that come on all of a sudden may include:

• A cough that produces foamy sputum that may be tinged with blood
• A feeling of suffocating or drowning
• Acute shortness of breath or difficulty breathing
• Anxiety, agitation or a sense of apprehension
• Chest pain, if pulmonary edema is caused by heart disease
• Excessive sweating
• Gasping for breath, wheezing , breathlessness
• Pale skin
• Rapid, irregular heartbeat, palpitations

Anyone experiencing these above-listed signs and symptoms should seek medical help as soon as possible. Pulmonary edema can result in death if the patient does not receive prompt treatment.

Signs and symptoms that develop more gradually are often due to heart failure.

They may include:

• Ankle edema or swelling of the legs.
• Difficulty in breathing with effort. This is more noticeable when lying flat as opposed to sitting up.
• Fatigue.
• Loss of appetite.
• Nocturia or frequent urination at night.
• Rapid weight gain. The weight gain is from accumulation of fluid in the body, especially in the legs. Pulmonary edema may develop as a result of congestive heart failure, a condition in which the heart pumps too little blood to meet the body's needs.
• Unusual shortness of breath during physical activity.
• Waking-up at night with a breathless feeling that may be relieved by sitting up.

Signs and symptoms of pulmonary edema caused by high-altitude generally include:

• Cough
• Fluid retention
• Headache
• Insomnia
• Shortness of breath

Acute pulmonary edema comes on suddenly and is life-threatening. Get emergency assistance if any of the following acute signs and symptoms appears:

• A bubbly, wheezing or gasping sound when breathing
• A severe drop in blood pressure
• Breathing difficulty along with excessive sweating
• Pink, frothy sputum when coughing. It is a classic sign of pulmonary edema
• Skin has a blue or gray tone
• Trouble breathing or a feeling of suffocating (dyspnea)
• Sudden worsening of any of the symptoms associated with chronic pulmonary edema or high-altitude pulmonary edema

What are the causes of pulmonary edema?

The lungs hold numerous small, elastic air sacs called alveoli. With each breath, these air sacs take in oxygen and release carbon dioxide. Usually, the exchange of gases occurs without problems.

But in certain conditions, the alveoli fill with fluid instead of air. This prevents the oxygen from being absorbed into the bloodstream.

Several factors can cause fluid to accumulate in the lungs. They are usually associated with the heart (cardiac pulmonary edema). The functions of heart and lungs are closely related.

The heart

It is composed of two upper and two lower chambers. The upper chambers are called the right and left atria. They receive incoming blood and pump it into the lower chambers. The lower chambers, through the ventricles, pump blood out of the heart. The heart valves keep blood flowing in the right direction.

The heart and the lungs

Usually, deoxygenated blood from all over your body enters the right atrium and flows into the right ventricle, where it is pumped through large blood vessels to the lungs. There, the blood releases carbon dioxide and picks up oxygen. The oxygen-rich blood then returns to the left atrium through the pulmonary veins, flows through the mitral valve into the left ventricle, and finally leaves the heart through another large artery, the aorta. The aortic valve at the base of the aorta keeps the blood from flowing backward into your heart. From the aorta, the blood travels to the rest of the body.

Cardiac pulmonary edema

Cardiac pulmonary edema is also known as congestive heart failure. It occurs when the overworked left ventricle is not capable of pumping out enough of the blood it receives from the lungs. As a result, pressure increases inside the left atrium and then in the pulmonary veins and capillaries. This causes fluid to be pushed through the capillary walls into the air sacs.

Congestive heart failure can also occur when the right ventricle is unable to overcome the amplified pressure in the pulmonary artery. This usually results from left heart failure, chronic lung disease or high blood pressure in the pulmonary artery (pulmonary hypertension).

Medical conditions that can cause weakness and failing of the left ventricle include:

• Coronary artery disease. Over time, the arteries that supply blood to the heart can become narrow from fatty deposits. A heart attack occurs when a blood clot forms in one of these narrowed arteries. There is blocking of the blood flow. This damages the section of the heart muscle supplied by that artery. The result is that the damaged heart muscle can no longer pump as well as it is supposed to.
  
  The rest of the heart tries to compensate. However, it is unable function efficiently or it is weakened by the added workload. When the pumping action of the heart is damaged, blood backs up into the lungs. As a result, fluid is forced to pass through the capillary walls and into the air sacs.


• Cardiomyopathy. It is a condition where the heart muscle is damaged by causes other than blood flow problems. Frequently, cardiomyopathy has no known cause. Although it is sometimes genetically inherited. Less common causes include viral infections (myocarditis), alcohol abuse and the toxic effects of drugs such as heroin and some types of chemotherapy.
  
  Cardiomyopathy weakens the left ventricle which is the heart's main pump. The heart may not be able to respond to conditions that require it to work harder (surge in blood pressure, a faster heartbeat with exertion or excess salt consumption that causes water retention or infections..) When the left ventricle cannot carry on with the demands, fluid backs up into the lungs.


• Heart valve. In mitral valve disease or aortic valve disease, the valves that regulate blood flow in the left side of the heart either do not open wide enough or do not close completely. This allows blood to flow backward through the valve. This condition causes greater stress on the coronary arteries.
  
  The increased pressure extends into the left atrium and then to the pulmonary veins, causing fluid to accumulate in the lungs. If the mitral valve leaks, some blood is backwashed toward the lung every time the heart pumps. If the leakage develops rapidly, sudden and severe pulmonary edema may develop.


• High blood pressure (hypertension) . Untreated or uncontrolled high blood pressure causes a thickening of the left ventricular muscle. It worsens coronary artery disease.

Noncardiac pulmonary edema

Pulmonary edema is not always caused by heart disease. This condition is known as noncardiac pulmonary edema because the heart is not the cause of the problem.

Some factors that can cause noncardiac pulmonary edema are:

• Lung infections. Such as pneumonia. The edema occurs only in the part of the lung that is irritated.


• Exposure to certain toxins. Inhaled toxins such as chlorine or ammonia.


• Kidney disease. When the kidneys cannot eliminate waste effectively, excess fluid can build up, causing pulmonary edema.


• Smoke inhalation. Smoke from a fire contains chemicals. They can damage the membrane between the air sacs and the capillaries, allowing fluid to enter the lungs.


• Adverse drug reaction. Many drugs, (illegal drugs, aspirin and chemotherapy drugs) are recognized to cause noncardiac pulmonary edema.


• Acute respiratory distress syndrome (ARDS) . This serious disorder occurs when the lungs suddenly fill with fluid and inflammatory white blood cells. Many conditions can cause ARDS, including severe injuries (trauma), systemic infection (sepsis), pneumonia and shock.


• High altitudes. High-altitude pulmonary edema (HAPE) typically occurs at elevations above 8,000 feet (about 2,400 meters). It can affect climbers, hikers or skiers who start exercising at higher altitudes without first becoming acclimated. Even people who have hiked or skied at high altitudes in the past are not immune.

The precise cause is not entirely clear. HAPE seems to develop as a result of increased pressure from constriction of the pulmonary capillaries. Without proper care, HAPE can be fatal.

Most people with pulmonary edema will be hospitalized for at least a few days, often longer.

After the condition has been stabilized, the patient might be referred to a specialist such as a cardiologist or a pulmonologist.

It is a good idea to prepare ahead of time for the first medical appointment and gather all the necessary information (list of symptoms, relevant personal information, copies of medical records, medications and vitamins, type of diet, preparing a list of questions to ask the doctor..).

Diagnosis of pulmonary edema

Pulmonary edema requires prompt treatment. Diagnosis is made on the basis of symptoms, physical exam and chest X-ray.

Several types of blood tests will be necessary:

A blood test from an artery on the wrist to check the amount of oxygen and carbon dioxide it contains. Blood will also be checked for levels of a substance called B-type natriuretic peptide (BNP). Increased levels of BNP may indicate that pulmonary edema is caused by heart problems. Other blood tests will usually be done, including tests of kidney function, blood count, and tests to exclude a heart attack as the cause of the pulmonary edema.

Once condition is stable, the patient's medical history will be reviewed especially for cardiovascular or lung disease. Other tests might include:

• X-ray. A chest X-ray will probably be the first test to confirm the diagnosis of pulmonary edema.


• Electrocardiography (ECG) . This noninvasive test can reveal a wide range of information about the heart. During an ECG, patches are attached to the patient´s skin and receive electrical impulses from the heart. These are recorded in the form of waves on graph paper or a monitor. The wave patterns show the heart rate and rhythm, and if areas of the heart show diminished blood flow.


• Echocardiography or diagnostic cardiac ultrasound exam. It is a noninvasive test. It uses high-frequency sound waves that are reflected from the tissues of the heart. The sound waves are then sent to a machine that uses them to compose images of the heart on a monitor.
  
  This test can help diagnose a number of heart problems, including valve problems, abnormal motions of the ventricular walls, fluid around the heart and congenital heart defects.


• Transesophageal echocardiography (TEE) . A soft, flexible tube with a special transducer tip is inserted through the mouth and into the esophagus. It allows a closer and more accurate picture of the heart and central pulmonary arteries. The patient is given a sedative. It might cause a sore throat for a few days after the procedure. There's a slight risk of perforation or bleeding from the esophagus.


• Pulmonary artery catheterization. If other tests fail to reveal the reason for pulmonary edema, this procedure measures the pressure in the lung capillaries. During this test, a small, balloon-tipped catheter is inserted through a vein in the leg or arm into a pulmonary artery.


• Cardiac catheterization. If the ECG or echocardiography fails to uncover the cause of the pulmonary edema, or if the patient has chest pain, heart catheterization with coronary angiogram may be suggested. During cardiac catheterization, a long thin tube called a catheter is inserted in an artery or vein in the groin, neck or arm and threaded through the blood vessels to the heart. If dye is injected during the test, it is referred to as a coronary angiogram. During this procedure, corrective action such as opening a blocked artery can be taken, which may quickly improve the pumping action of the left ventricle. Cardiac catheterization can also be used to measure the pressure in the heart chambers, evaluate the heart valves, and look for causes of pulmonary edema.

What is the treatment for pulmonary edema?

Giving oxygen is the first step in the treatment for pulmonary edema. It should relieve some of the symptoms. Sometimes it may be necessary to assist breathing with a machine.

Depending on the patient´s condition and the reason for the pulmonary edema, treatment may include one or more of the following medications:

• Preload reducers. Nitroglycerin and diuretics (such as furosemide (Lasix)) are commonly used to treat pulmonary edema. These medications dilate the veins in the lungs and elsewhere in the body. This decreases fluid pressure going into the heart and lungs. Diuretics initially induce frequent urination. A catheter might be temporarily needed while in the hospital.


• Morphine (Astramorph, Roxanol) . This narcotic may be used to relieve shortness of breath and anxiety. However, there is debate on whether the risks of morphine outweigh the benefits.


• Afterload reducers. These drugs dilate the peripheral vessels and take a pressure load off the left ventricle. Some examples of afterload reducer medications include nitroprusside (Nitropress), enalapril (Vasotec) and captopril (Capoten).


• Blood pressure medications. If there is high blood pressure when developing pulmonary edema, these medications will help control it. On the other hand, if blood pressure is too low, drugs to raise it will be given.

Treating high-altitude pulmonary edema (HAPE)

If there are mild symptoms of HAPE when climbing or traveling at high altitudes, descending a few thousand feet (about 600 to 900 meters) should relieve symptoms. Also, oxygen is helpful. Because HAPE can be life-threatening, a helicopter rescue may be necessary for the most serious cases.

To help treat or prevent symptoms of HAPE, some climbers take the prescription medication acetazolamide (Diamox). This medication can occasionally have side effects (tingling or burning in the hands and feet, diarrhea, confusion, nausea, loss of appetite, and hearing problems).

Possible complications of pulmonary edema

If pulmonary edema is not treated, it can raise pressure in the pulmonary artery and eventually the right ventricle begins to fail. The increased pressure backs up into the right atrium and then into various parts of your body, where it can cause:

• Abdominal swelling
• Buildup of fluid in the membranes that surround the lungs (pleural effusion)
• Congestion and swelling of the liver
• Leg swelling (edema)

When not treated, acute pulmonary edema can be fatal.

In some cases it may be fatal even if treatment is received.

Recovery and preventing recurrence

The following suggestions may speed recovery from cardiac pulmonary edema and help prevent a recurrence:

• Check Weight daily. Keeping a record of daily weight (in the morning before breakfast). Seek medical advice if there is a gain of 2 to 3 pounds (about 4 to 7 kilograms) in a single day.


• Controlling high blood pressure. Checking blood pressure with a home cuff at least once a day.


• Diet. Typically, people with pulmonary edema will need to follow a low-salt diet.


• Medical advice. Follow medical advice about controlling any underlying health problems, including guidance on diet, weight and exercise.


• Plenty of sleep. If feeling tired, napping during the day is recommended. Lung function may take as long as three to six months before returning to normal.

In the case of noncardiac pulmonary edema and some forms of ARDS, any further damage to the lungs should be minimized. Avoid drugs, allergens or high altitudes.

Prevention of pulmonary edema

Some of these measures can help reduce the risk of pulmonary edema:

Preventing cardiovascular disease

Cardiovascular disease is the leading cause of pulmonary edema.

• Control blood pressure. High blood pressure (hypertension) can lead to serious conditions such as stroke, cardiovascular disease and kidney failure. Most adults should take just a few minutes to have their blood pressure checked at least once every two years.
  
  A resting blood pressure reading below 120/80 millimeters of mercury (mm Hg) is considered normal. Blood pressure of consistently 140/90 mm Hg or higher, is an indication of high blood pressure. A reading in between these levels is in the prehypertensive category.
  
  In many cases, blood pressure can be lowered or maintained at a healthy level by getting regular exercise, eating a diet rich in fresh fruits, vegetables and low-fat dairy products, and limiting salt and alcohol.


• Blood cholesterol. Elevated cholesterol levels can cause fatty deposits to form in the arteries. This alters blood flow and increases the risk of vascular disease. But lifestyle changes can often keep cholesterol levels low. This includes limiting fats (especially saturated fats) eating more fiber, fish, and fresh fruits and vegetables, exercising regularly, stopping smoking, and drinking in moderation.


• Smoking. Smoking increases the risk of a second heart attack or heart-related death and also increases risk of lung cancer and other lung problems such as emphysema. In addition, exposure to secondhand smoke is a contributing factor to coronary artery disease.


• A heart-healthy diet. A diet rich in omega-3 fatty acids (found in fish) helps improve blood cholesterol levels and prevent blood clots. It is also important to eat plenty of fruits and vegetables, which contain antioxidants, vitamins and minerals. Reduce fat intake, especially animal (saturated) and trans fats (hydrogenated oils).


• Low-salt diet. Limit the use of salt (sodium). In some people with severely damaged left ventricular function, excess salt (even in a single meal or a bag of chips) may be enough to trigger congestive heart failure.


• Exercise regularly. Exercise is vital for a healthy heart. Regular aerobic exercise (about 30 minutes a day), helps control blood pressure and cholesterol levels, and maintain a healthy weight.


• Control weight. Being even slightly overweight increases the risk of cardiovascular disease. On the other hand, losing small amounts of weight can lower blood pressure, cholesterol and reduce the risk of diabetes.


• Taking baby aspirin. Seek medical advice about the pros and cons of taking one baby aspirin (81 milligrams) a day.


• Manage stress. To reduce the risk of heart problems, try to decrease stress levels.

Preventing HAPE (high-altitude pulmonary edema)

If traveling or climbing at high altitudes, gradual adaptation is necessary. Most experts advise ascending no more than 1,000 or 2,000 feet (300 to 600 meters) a day, once you reach 8,000 feet (about 2,400 meters). In addition, it is important to drink plenty of water to stay hydrated. Being physically fit will not necessarily prevent HAPE. The medication acetazolamide (Diamox) can help prevent HAPE (taken 12 to 72 hours before travelling to a high altitude). It is advised to continue the medication for an extra few days if there are any signs of altitude sickness (especially headache or insomnia).

Written by Stephanie Brunner B.A.


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