Diagnosis of Chronic Obstructive Pulmonary Disease (COPD)
None of the current methods used to diagnose COPD can detect the disease before irreversible lung damage has occurred. But the earlier it is detected, the sooner steps can be taken to modify further damage. When you first see your doctor, he or she will ask about your symptoms and medical history and will perform a physical exam. The history and physical exam provide the most important information that is used for the diagnosis of COPD.
If your doctor suspects you might have COPD, you may undergo one or more of the following tests:
Many tests of lung function have been developed, and each provides slightly different information about how well your lungs are working. Pulmonary function tests are painless, noninvasive tests that are performed using a machine called a spirometer. By breathing into the spirometer under certain conditions, the doctor can measure your lung volume and your ability to move air in and out of your lungs in a certain period of time. Your results are compared with typical findings of a healthy person your age and height, and the doctor can then determine to what extent your lung function is diminished. Sometimes, tests are repeated after you have been given a bronchodilator medication, to see if your results improve with this type of treatment.
Pulmonary function tests include:
Forced Vital Capacity (FVC) —This is the maximum volume of air that can be forcibly exhaled after inhaling as deeply as possible.
Residual Volume (RV) —This is the amount of air that remains in the lungs when measuring vital capacity. In persons with COPD, RV is usually increased dramatically from normal because air is trapped in the damaged lung and cannot be exhaled normally.
Total Lung Capacity (TLC) —This is the total amount of air the lungs are capable of holding and is the combination of FVC and RV.
Forced Expiratory Volume in 1 Second (FEV1) —This measures the volume of air that can be forcibly exhaled in one second and represents the rate of air movement out of the lungs. FEV1 typically declines a very small amount per year in normal persons, but the decline can be several times over the expected in people with COPD. A greater than expected annual fall in FEV1 is the most sensitive test for COPD and a reasonably good predictor of disability and early death.
Carbon Monoxide Diffusing Capacity
This test measures how well your lungs transfer a small amount of carbon monoxide gas into your blood. You take a breath of air containing a very small amount of carbon monoxide from a container, and the amount of carbon monoxide in your exhaled air or arterial blood is then measured.
A sensor on your finger is used to acquire quick, basic information about the amount of oxygen in your blood. More detailed measurements are provided by the blood test called an arterial blood gas.
Arterial Blood Gases
Arterial blood gases determine the amount of oxygen and carbon dioxide in your bloodstream. This test requires that a blood sample be removed from one of your arteries, usually in the wrist, but sometimes in the groin. It is done more often in an emergency room or hospital setting for someone who appears more seriously ill.
Collecting a sputum specimen (a sample of coughed-up mucus) for laboratory testing can reveal the presence of an infection that could be complicating COPD.
This test provides a detailed x-ray of the lungs and can be useful in assessing the extent of lung damage associated with COPD.
Levels of Alpha-1-Antitrypsin
This blood test measures levels of alpha-1-antitrypsin, which is an important protein that helps protect the lungs from damage due to inflammation. Persons who develop COPD at an early age or who develop the disease but never smoked may have abnormally low levels of this protein due to a genetic defect. The substance can be replaced artificially by giving the medicine Prolastin by vein once a week. Prolastin is very expensive.
American Lung Association website. Available at: http://www.lungusa.org/site/pp.asp c=dvLUK9O0E&b=22542.
National Heart, Lung and Blood Institute website. Available at: http://www.nhlbi.nih.gov/ .
Last reviewed June 2008 by
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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