Spirometry is among the first, and one of the most noninvasive, tests used to diagnose lung diseases or disorders, including COPD. In this test, a machine (a spirometer) measures how much air you can breathe in, and then how much and how forcefully you can exhale that air back out in a set matter of seconds. The test measures how well the lungs work. Results are recorded and displayed in a graphic, which will be examined by a specialist before results are reported.
Here is some information as to what you have to do, and to expect, when taking this test.
Before the test
- Whether you are taking bronchodilators (drugs that relax muscles around airways and make breathing easier) or not, you may be use asked to use one before the test, or to use one at some point during the test to see if results change. Conversely, you may be asked to stop using a bronchodilator before the test, as well.
- You should wear comfortable and loose clothes that doesn’t interfere with your ability to take a deep breath.
- Avoid eating heavy meals, smoking, drinking alcohol, or doing heavy physical exercise before the test.
During the test
Usually, you are seated with a clip on your nose to avoid air from escaping. Or, you may be asked to stand. During the test, you’ll have to take a deep breath and blow the air out as hard and fast as you can to a mouthpiece connected, through a tube, to a machine. You want to empty your lungs completely.
This test is usually is repeated at least three times to make sure that the results are consistent.
If you have to inhale a bronchodilator, you’ll have to wait at least 15 minutes before you do the test again. Here, the doctor compares the results of different measurements (with and without bronchodilators) to see if improvement registers.
Spirometry results explained
The machine measures how much air you can breath out of your lungs. The two main measures include:
- Forced vital capacity (FVC). This is the amount of air that you breathe out in one complete breath (six seconds or more).
- Forced expiratory volume (FEV-1). This is the amount of air that you breathe out in the first second.
The results (in percentage) are compared to those of someone of your age, gender, height, and race. People with COPD have FEV-1/FVC of less than 80% of predicted value (moderate COPD). If FEV-1/FVC is less than 50%, COPD is likely to be diagnosed as severe.
Potential side effects
Spirometry is a safe and relatively easy test. However, some people may feel lightheaded, tired, dizzy, or experience shortness of breath after taking the test.
Most people are not bothered by this test. But it does increase pressure inside of your head, chest, stomach, and eyes as you breathe out. For those with heart conditions or recent surgeries to those areas, the test may not be recommended.
A spirometry test is also used to detect other lung conditions, such as asthma, bronchitis and emphysema (the latter two closely associated with COPD), or to detect other reasons for shortness of breath.
One of the advantages of this test is that it can detect the disease even before symptoms are fully evident. It can also track the severity of COPD and its progression (changes in disease states).
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