Lung diffusion testing

• Alternative Names

  Diffusing capacity; DLCO test

• How the test is performed

  You breathe in (inhale) air containing a very small amount of a tracer gas, such as 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 tracer gas 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 - 6 hours before the test.
  • If you use a bronchodilator or inhaler medications, ask your health care provider whether or not you can use them before the test.
• How the test will feel

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

• Why the test is performed

  The test is used to diagnose certain lung diseases, and in persons with established lung disease. Repeatedly measuring the diffusing capacity can help determine whether the disease is improving or getting worse.

• Normal Values

  Normal test results depend on a person's:

  • Age
  • Gender
  • Height
  • Hemoglobin (the protein in red blood cells that carries oxygen) level
• What abnormal results mean

  Abnormal results 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:

  • Emphysema
  • Interstitial fibrosis
  • Pulmonary hypertension
  • Sarcoidosis
• What the risks are

  There are no significant risks.

• Special considerations

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

• References

  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.

Review Date: 10/14/2009

Reviewed By: Andrew Schriber, MD, FCCP, Specialist in Pulmonary, Critical Care, and Sleep Medicine, Virtua Memorial Hospital, Mount Holly, New Jersey. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.