Pulmonary edema occurs when fluid accumulates in the air sacs of the lungs - the alveoli - making it difficult to breathe. This interferes with gas exchange and can cause respiratory failure.

Pulmonary edema can be acute (sudden onset) or chronic (occurring more slowly over time). If it is acute, it is classed as a medical emergency needing immediate attention.

The most common cause of pulmonary edema is congestive heart failure, where the heart cannot keep up with the demands of the body.

Treatment of pulmonary edema usually focuses on improving respiratory function and dealing with the source of the problem. It generally includes providing additional oxygen and medications to treat the underlying conditions.

Fast facts on pulmonary edema

  • Pulmonary edema is a condition involving fluid buildup in the lungs.
  • Sudden onset (acute) pulmonary edema is a medical emergency.
  • Symptoms include shortness of breath, cough, decreased exercise tolerance or chest pain.

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Pulmonary edema can be acute or chronic.

To raise the patient's blood oxygen levels, oxygen is given either through a face mask or prongs - tiny plastic tubes in the nose. A breathing tube may be placed into the trachea if a ventilator, or breathing machine, is necessary.

If tests show that the pulmonary edema is because of a problem in the circulatory system, the patient will be treated with intravenous medications to help remove fluid volume and control blood pressure.

During normal breathing, the small air sacs in the lungs - alveoli - fill up with air. Oxygen is taken in, and carbon dioxide is expelled. Pulmonary edema occurs when the alveoli are flooded.

When the alveoli are flooded, two problems occur:

  1. The bloodstream cannot get enough oxygen.
  2. The body is unable to get rid of carbon dioxide properly.

Common causes include:

Besides direct injury to the lungs, as in ARDS, other causes include:

  • brain injuries such as brain bleeding, stroke, head injury, brain surgery, tumor, or seizure
  • high altitude
  • blood transfusion

Cardiogenic pulmonary edema

Pulmonary edema that is due to a direct problem with the heart is called cardiogenic.

Congestive heart failure is a common cause of cardiogenic pulmonary edema; in this condition, the left ventricle cannot pump out enough blood to meet the needs of the body.

This causes a buildup of pressure in other parts of the circulatory system, forcing fluid into the air sacs of the lungs and other parts of the body.

Other heart-related problems that can lead to pulmonary edema include:

  • Fluid overload - this can result from kidney failure or intravenous fluid therapy.
  • Hypertensive emergency - a severe increase in blood pressure that puts excessive strain on the heart.
  • Pericardial effusion with tamponade - a buildup of fluid around the sac that covers the heart. This can decrease the heart's ability to pump.
  • Severe arrhythmias - this can be tachycardia (fast heartbeat) or bradycardia (slow heartbeat). Either can result in poor heart function.
  • Severe heart attack - this can damage the muscle of the heart, making pumping difficult.
  • Abnormal heart valve - can affect the flow of blood out of the heart.

Causes of pulmonary edema that are not due to poor heart function are called noncardiogenic; they are typically caused by ARDS (acute respiratory distress syndrome). This is a severe inflammation of the lungs that leads to pulmonary edema and significant breathing difficulties.

Acute pulmonary edema causes significant breathing difficulties and can appear without warning. This is an emergency and requires immediate medical attention. Without proper treatment and support, it can be fatal.

Along with breathing difficulties, other signs and symptoms of acute pulmonary edema can include:

  • cough, often with a pink frothy sputum
  • excessive sweating
  • anxiety and restlessness
  • feelings of suffocation
  • pale skin
  • wheezing
  • rapid or irregular heart rhythm (palpitations)
  • chest pain

If the pulmonary edema is chronic, symptoms are normally less severe until the body's system can no longer compensate. Typical symptoms include:

  • difficulty breathing when lying flat (orthopnea)
  • swelling (edema) of feet or legs
  • rapid weight gain due to the accumulation of excess fluid
  • paroxysmal nocturnal dyspnea - episodes of severe sudden breathlessness at night
  • fatigue
  • increased breathlessness with physical activity

Pulmonary edema happens when fluid collects inside the lungs, in the alveoli, making it hard to breathe. Plural effusion also involves fluid in the lung area, and it is sometimes called "water on the lungs."

However, in pleural effusion, water fluid collects in the layers of the pleura that are ouside the lungs. It can result from heart failure, cirrhosis, or a pulmonary embolism. It can also occur after heart surgery.

Pulmonary edema can overlap with pneumonia, but it is a different condition. Pneumonia is an infection that often occurs as a complication of a respiratory infection, such as the flu.

It can be difficult to distinguish between the two. If the individual or a family member can provide a detailed medical history, this will make it easier for a physician to make the correct diagnosis and provide the right treatment.

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Sometimes, a chest X-ray can assist in the diagnosis of pulmonary edema.

The patient will undergo a physical exam first. The doctor will use a stethoscope to listen to the lungs for crackles and rapid breathing, and the heart for abnormal rhythms.

Blood tests will be carried out to determine blood oxygen levels; the doctor will often order other blood tests, including:

  • electrolyte levels
  • kidney function
  • liver function
  • blood counts and blood markers of heart failure

An ultrasound of the heart, an echocardiogram, and an electrocardiogram (EKG) can help determine the condition of the heart.

A chest X-ray may be used to see whether there is any fluid in or around the lungs and to check the size of the heart. A CT scan of the chest may also be ordered.

Patients with an increased risk of developing pulmonary edema must follow their doctor's advice to keep their condition under control.

If congestive heart failure is the problem, following a healthy, well-balanced diet, and maintaining a healthy body weight can help reduce the risk of future episodes of pulmonary edema.

Regular exercise also improves heart health as does:

  • Reducing salt intake - excess salt can lead to water retention. This increases the work the heart has to do.
  • Lowering cholesterol levels - high cholesterol can lead to fatty deposits in the arteries, which, in turn, increases the risk of heart attack and stroke and therefore pulmonary edema.
  • Smoking cessation - tobacco increases the risk of a number of diseases, including heart disease, lung disease, and circulatory problems.

Altitude-induced pulmonary edema can be minimized by making a gradual ascent, taking medications before traveling, and avoiding excess exertion while progressing to higher altitudes.