Pulmonary Edema

  • Medical Author:
    Siamak N. Nabili, MD, MPH

    Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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How is pulmonary edema diagnosed?

Pulmonary edema is typically diagnosed by a chest X-ray. A normal chest radiograph (X-ray) consists of a central white area pertaining to the heart and its main blood vessels plus the bones of the vertebral column, with the lung fields showing as darker fields on either side, enclosed by the bony structures of the chest wall.

A typical chest X-ray with pulmonary edema may show a more white appearance over both lung fields than usual. More severe cases of pulmonary edema can demonstrate significant opacification (whitening) over the lungs with minimal visualization of the normal lung fields. This whitening represents filling of the alveoli as a result of pulmonary edema, but it may give minimal information about the possible underlying cause.

To identify the cause of pulmonary edema, a thorough assessment of the patient's clinical picture is essential. A careful medical history and physical examination often provide invaluable information regarding the cause.

Other diagnostics tools used in assessing the underlying cause of pulmonary edema include the measurement of plasma B-type natriuretic peptide (BNP) or N-terminal pro-BNP. This is a protein marker (a hormone) that will rise in the blood due to the stretch of the chambers of the heart. Elevation of the BNP nanogram (one billionth of a gram) per liter greater than a few hundred (300 or more) is highly suggestive of cardiac pulmonary edema. On the other hand, values less than 100 essentially rule out heart failure as the cause.

More invasive methods are occasionally necessary to distinguish between cardiac and noncardiac pulmonary edema in more complicated and critical situations. A pulmonary artery catheter (Swan-Ganz) is a thin, long tube (catheter) inserted into the large veins of the chest or the neck and advanced through the right-sided chambers of the heart and lodged into the pulmonary capillaries (small branches of the blood vessels of the lungs). This device has the capability of directly measuring the pressure in the pulmonary vessels, called the pulmonary artery wedge pressure.

  • A wedge pressure of 18 mmHg or higher is consistent with cardiogenic pulmonary edema,
  • whereas a wedge pressure of less than 18 mmHg usually favors a non-cardiogenic cause of pulmonary edema.

A Swan-Ganz catheter placement and data interpretation is done only in the intensive care unit (ICU) setting.

Medically Reviewed by a Doctor on 5/7/2015
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