COPD Diagnostic Tests: Pulmonary Function, Spirometry, and More
Your Specific Lung Function Test Results
You might hear an individual with COPD say, "I have only 30 percent lung function." They are probably referring to their FEV1 value.
Example: If the predicted normal FEV1 is 3.0 liters and your FEV1 is 1.0 liter, your percent of the expected normal value would be 33 percent. Understanding your test results can be difficult, but here is what you need to know as you review your FEV1 results: the FEV1 is a good way of tracking if someone''s condition has stabilized or is worsening.
COPD severity is often graded using percentage of predicted FEV1 after you have inhaled a bronchodilator medicine. These grades help health care providers in suggesting the right kind of treatments for each of the disease stages.
Chest X-ray and CT Evaluations
Routine chest X-rays are familiar to most people. They are performed by standing or sitting with the front of your chest pressed against an X-ray plate. You are asked to take a deep breath and hold it while an X-ray tube exposes the film in a plate pressed against your chest.
Often a side view of the chest is included. Unfortunately, the routine chest X-ray is a poor test for evaluating COPD unless dramatic changes are present. One such change would be the presence of large bubbles of empty lung issue called "bullae." The changes noted on an X-ray are primarily at the bottom of the lungs where flattened diaphragms may be shown. Changes may also be seen on the side view if there is trapped air between the breast bone and the heart. The routine chest X-ray can show air trapping by showing an increased chest diameter.
The best test currently available for diagnosing emphysema and bronchiectasis is the computed tomogram (CT) of the lungs, often called a CT scan. Specifically, high-resolution CT (HRCT) scans of the chest are the most sensitive tests for detecting and measuring emphysema. This test is a high-tech variation of the ordinary chest X-ray. It can show much more detail. It is used to calculate the amount of lung tissue and air in how severe it is.
An HRCT scan of the chest can detect emphysema even in people whose lung function is normal. This scan can also detect other problems that a normal chest X-ray might miss. These include areas of fibrosis, small lung nodules and even small lung cancers. However, the radiation dose you receive during such a study is the same as the radiation dose you''d receive from having about 14 regular chest X-rays.
HRCT is also excellent at detecting and determining the severity of bronchiectasis. This is another lung disease sometimes associated with COPD. In bronchiectasis, the lung''s bronchial tubes are damaged and expanded. Thickening of the bronchial walls can also be seen with HRCT. This can help determine how much chronic bronchitis is present in the lungs.