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Lung diffusion testing

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Lung diffusion testing
Lung diffusion testing

Alternative Names    Return to top

Diffusing capacity; DLCO test

Definition    Return to top

Lung diffusion testing looks at how well gases are passing from the air sacs of the lungs into the blood, to determine whether the lung is sending enough oxygen into the blood. The test measures the "diffusing capacity of the lung for carbon monoxide" or DLCO.

How the Test is Performed    Return to top

You breathe in (inhale) some gas containing a very small amount of carbon monoxide. You hold your breath for 10 seconds, then rapidly blow it out (exhale). The exhaled gas is tested to determine how much of the carbon monoxide was absorbed during the breath.

How to Prepare for the Test    Return to top

How the Test Will Feel    Return to top

The mouthpiece fits tightly around your mouth. Clips are put on the nose.

Why the Test is Performed    Return to top

The test is used to diagnose certain lung diseases. It may also be used to see how gases move from the lungs into the bloodstream.

Normal Results    Return to top

Normal test results depend on a person's:

What Abnormal Results Mean    Return to top

Abnormal results usually mean that gases do not move normally across the lung tissues into the blood vessels of the lung. This may be due to lung diseases such as:

Risks    Return to top

There are no significant risks.

Considerations    Return to top

Other pulmonary function tests may be done together with this test.

References    Return to top

Reynolds, HY. Respiratory Structure and Function: Mechanisms and Testing. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 85.

Update Date: 9/13/2008

Updated by: Benjamin Medoff, MD, Assistant Professor of Medicine, Harvard Medical School, Pulmonary and Critical Care Unit, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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