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Lung diffusion testing

Alternative names

Diffusing capacity; Diffusion capacity; DLCO test


Lung diffusion testing is used to determine how well oxygen passes from the air sacs of the lungs into the blood.

How the test is performed

You inhale a single breath from a volume of gas containing a known small quantity of carbon monoxide , hold your breath for 10 seconds, then rapidly exhale. The exhaled gas is then analyzed to determine the amount of carbon monoxide that was absorbed during the breath.

How to prepare for the test

Do not eat a heavy meal before the test. Do not smoke for at least 4 to 6 hours prior to the test. Specific instructions will be given if bronchodilators or inhaler medications should not be used before the test.

For infants and children:
The preparation you can provide for this test depends on your child's age and experience. For specific information regarding how you can prepare your child, see the following topics:
  • infant test or procedure preparation (birth to 1 year)
  • toddler test or procedure preparation (1 to 3 years)
  • preschooler test or procedure preparation (3 to 6 years)
  • schoolage test or procedure preparation (6 to 12 years)
  • adolescent test or procedure preparation (12 to 18 years)

How the test will feel

There is a tight fitting mouth piece to breathe through, and nose clips are applied.

Why the test is performed

The test is performed to determine the presence and extent of certain lung diseases that affect how well gases cross from the air sacs into the bloodstream.

Normal Values

This test is usually reported as the percent of predicted amount of carbon monoxide inhaled that should be absorbed, according to the age, sex, and height of the person.

What abnormal results mean

Abnormal results generally indicate that gases do not diffuse normally across lung membranes. This may indicate that certain lung diseases are present. Some of these diseases are diffuse interstitial fibrosis , sarcoidosis , asbestosis , and emphysema .

What the risks are

There are no significant risks.

Special considerations

Other pulmonary function tests may be done in combination with this test.

Update Date: 10/22/2003

Allen J. Blaivas, D.O., Division of Pulmonary, Critical Care, and Sleep Medicine, University Hospital, Newark, NJ. Review provided by VeriMed Healthcare Network.

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Last updated: Tue, 06 Jan 2009 00:20:03 GMT