Lung diffusion testing
Diffusing capacity; DLCO testLung diffusion testing measures how well the lungs exchange gases. This is an important part of lung testing, because the major function of the lungs is to allow oxygen to diffuse or pass into the blood from the lungs, and to allow carbon dioxide to diffuse from the blood into the lungs.
Lung testing
Pulmonary function tests are a group of tests that measure breathing and how well the lungs are functioning.
How the Test is Performed
You breathe in (inhale) air containing a very small amount of carbon monoxide and a tracer gas, such as methane or helium. 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.
Carbon monoxide
Carbon monoxide is an odorless gas that causes thousands of deaths each year in North America. Breathing in carbon monoxide is very dangerous. It i...
How to Prepare for the Test
Before taking this test:
- Do not eat a heavy meal before the test.
- Do not smoke for at least 4 to 6 hours before the test.
- If you use a bronchodilator or other inhaled medicines, 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 your nose.
Why the Test is Performed
The test is used to diagnose certain lung diseases, and to monitor the status of people with established lung disease. Repeatedly measuring the diffusing capacity can help determine whether the disease is improving or getting worse.
Normal Results
Normal test results depend on a person's:
- Age
- Sex
- 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:
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COPD
COPD
Chronic obstructive pulmonary disease (COPD) is a common lung disease. Having COPD makes it hard to breathe. There are two main forms of COPD:Chroni...
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Interstitial fibrosis
Interstitial fibrosis
Interstitial lung disease (ILD) is a group of lung disorders in which the lung tissues become inflamed and then damaged.
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Pulmonary embolism
Pulmonary embolism
A pulmonary embolus is a blockage of an artery in the lungs. The most common cause of the blockage is a blood clot.
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Pulmonary hypertension
Pulmonary hypertension
Pulmonary hypertension is high blood pressure in the pulmonary arteries of the lungs. It makes the right side of the heart work harder than normal....
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Sarcoidosis
Sarcoidosis
Sarcoidosis is a disease in which inflammation occurs in the lymph nodes, lungs, liver, eyes, skin, and/or other tissues.
ImageRead Article Now Book Mark Article - Bleeding in the lung
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Asthma
Asthma
Asthma is a chronic disease that causes the airways of the lungs to swell and narrow. It leads to breathing difficulty such as wheezing, shortness o...
ImageRead Article Now Book Mark Article - Reduced lung volume (capacity)
Risks
There are no significant risks.
Considerations
Other pulmonary function tests may be done together with this test.
Pulmonary function tests
Pulmonary function tests are a group of tests that measure breathing and how well the lungs are functioning.
References
Bhakta NR, Kaminsky DA. Pulmonary function testing: Physiologic and technical principles. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 31.
Scanlon PD, Niven AS. Respiratory testing and function. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 73.
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Lung diffusion testing - illustration
Lung diffusion testing measures how well oxygen passes from the air sacs in the lungs into the blood.
Lung diffusion testing
illustration
Review Date: 11/25/2023
Reviewed By: Denis Hadjiliadis, MD, MHS, Paul F. Harron Jr. Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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