What Is Spirometry and Why It Is Done
Spirometry is the most common type of pulmonary function or breathing test. This test measures how much air you can breathe in and out of your lungs, as well as how easily and fast you can the blow the air out of your lungs.
Your doctor may order spirometry if you have wheezing, shortness of breath, or a cough. This can help diagnose problems like asthma and COPD, or can be done to check lung function before a surgery. You may also have spirometry done if you are being treated for a chronic lung disease, such as COPD, asthma, or pulmonary fibrosis, to determine if your disease is improving or worsening and whether your medications or inhalers are working properly. Spirometry can be done in the doctor’s office or in a special pulmonary function testing lab.
What to Expect
On the day of the test, you may be asked to not use certain inhalers or medications. Wear loose clothing and avoid big meals before testing.
These tests are not painful. They are performed by a pulmonary function technician. The tests are repeated several times to make sure the results are accurate. When performing the test, keep the following in mind:
- You should take your daily medications prior to testing unless told otherwise.
- Do not smoke for at least six hours prior to testing.
- If you are taking a short-acting inhaler that is used only as needed, do not use for six to eight hours prior to testing, if possible.
- Your doctor may give you other instructions regarding medications.
During the test, you will be sitting upright. A clip is placed on your nose and you will be given a plastic mouthpiece connected to the spirometry machine. You will place your lips tightly around the mouthpiece and be asked to take in as big and deep a breath as possible and then blow out as hard and fast as you can. This maximal effort is very important, and testing will be repeated at least three times to get the best results.
The technician may give you a medicine to help open your airways and then repeat the test to see if your breathing improves with the medicine. The testing takes about 30 to 45 minutes.
Understanding the Results and What Happens Next
Spirometry will give your doctor information about why you may have a cough, shortness of breath, or noisy breathing and help diagnose certain lung problems. After the test, you can return to your normal daily activities.
Normal values are calculated based on age, height and gender. If a value is abnormal, a lung problem may be present. Sometimes a patient with normal lungs may have a breathing test value that is abnormal. Your doctor will explain what your test results mean. Depending on the results of the test, your doctor may prescribe inhalers or medicines to help improve your lung function. The testing may be repeated at future visits to monitor your lung function.
What Are the Risks and When It Should Not Be Done?
During the test, breathing fast and hard can make you feel tired, cough, feel dizzy or light-headed, or have chest tightness or pain. You should let the technician know if you have any discomfort.
You should let your doctor know if you've had a heart attack within the past month. You should also tell your doctor if you have had recent eye, chest or abdominal surgery, have had a collapsed lung or have tuberculosis. If you’ve had any of these, your doctor may wait until you recover before doing the testing.
Special steps are taken to avoid spreading germs between patients who use the same lung function equipment. The technician will change mouthpieces and other equipment between patients. Special filters are also used to prevent the spread of germs.
Be sure to ask if you have any questions before the test is started.
This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.
Approved by Scientific and Medical Editorial Review Panel. Last reviewed May 31, 2017.