When—and Why—to Have a Spirometry Test
To help identify chronic obstructive pulmonary disease (COPD) at its earliest stages before it causes serious lung damage, anyone at risk for the disease should take a simple, painless, noninvasive breathing test called spirometry at the first sign of any breathing difficulties.
Cigarette smoking causes the vast majority of COPD cases and the incidence rises with age. About one in 2,500 people worldwide has a genetic defect, alpha-1 antitrypsin deficiency, that increases risk, especially in younger smokers. Other factors that increase risk include a famly history of COPD, male gender (although the condition is often not suspected in women), respiratory illnesses in childhood, and work-related exposure to pollutants.
Spirometry will confirm or exclude a COPD diagnosis. This lung function test is performed in your doctor's office or in a pulmonary function laboratory and measures the amount of air you can blow out of your lungs and how fast you can blow it out. These measurements, taken with a machine called a spirometer, help the doctor determine how well your lungs are working and whether you may have COPD. Some spirometers are hand held while others are stationary.
To perform the test, you will be asked to take as deep a breath as you can, and to then blow out as hard and as fast as you can into a disposable mouthpiece that is connected to the spirometer with a flexible tube. At least three separate attempts are typically made, up to a maximum of eight. After reviewing the results and comparing them to the predicted values of a healthy individual of the same age, sex, height and race, an assessment can be made as to whether you have COPD or not.
The spirometer provides several key measurements that will determine whether you have COPD and its severity. The two most important values are forced vital capacity (FVC) and forced expiratory volume in one second (FEV1):
- FVC is a measure of the total volume of air exhaled.
- FEV1 measures the amount of air expelled from the lungs in the first second of a forced exhalation.
Measurements of 50 percent to 80 percent of predicted value for your age and gender indicate moderate COPD; measurements of 30 percent to 49 percent indicates severe COPD; and measurements of 30 percent or less indicate very severe COPD. The spirometer calculates these values automatically, along with the ratio between them, FEV1/FVC.
Some portable office spirometers measure FEV1 and the total amount you exhaled in six seconds (FEV6). On these spirometers, FEV6 is used as a substitute for FVC.