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COPD Diagnostic Tests: Pulmonary Function, Spirometry, and More

WebMD Medical Reference from the COPD Foundation


Doctors may make a diagnosis from reported symptoms and findings from the physical exam. For many conditions, however, a diagnosis cannot be made without conducting tests. This is especially true for lung diseases.

Individuals with COPD are often diagnosed with "pulmonary emphysema." This means the air sacs, or "alveoli," of the lungs are damaged. These tiny sacs cannot be seen directly in a physical exam. So, health care providers depend on a series of tests. These tests help them diagnose and evaluate the seriousness of this and other lung problems. These tests include X-rays or CT scans of the chest, pulmonary function testing (PFTs), and oximetry or arterial blood gas testing.

Oximetry and arterial blood gas testing evaluate the gases exchanged in the lungs. Some doctors suggest that newly diagnosed COPD patients have complete pulmonary function testing, including a diffusing capacity (DLCO) test. This test can be repeated on later visits, if a change is noted in your symptoms or the findings on an exam.

Some doctors recommend this test be done once per year. More testing may be needed to evaluate new treatments. More testing is also needed for individuals who appear to have health problems that are quickly getting worse.

Some doctors may order an initial or "baseline" high-resolution CT (HRCT) scan of the chest for COPD patients. The baseline HRCT scan can later be compared with future scans that may be done if the patient''s symptoms change. The HRCT is also the most sensitive method available for detecting emphysema.

In the following pages, we provide descriptions of the tests used most often for diagnosing and following the progress of lung diseases.

Pulmonary Function Testing (PFTs)

As the name implies, pulmonary function tests (PFTs) measure how well the lungs are moving air in and out. They also measure how well the lungs are moving oxygen to the blood. These breathing tests use special equipment and are done by trained staff in a hospital or office setting. Most are done by blowing into a tube while you sit in a chair.

Individuals with COPD often have abnormal PFT results which suggest airway blockage and air trapping. Similar changes can be seen in some other lung conditions, such as asthma. If the lung function testing includes a diffusing capacity (DLCO) test, a low value suggests emphysema.

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