Patient education: Spirometry (The Basics)

What is spirometry? — Spirometry is a type of breathing test (figure 1). It measures how well your lungs are working. Breathing tests might also be called "pulmonary function tests," or "PFTs."

Spirometry measures:

●How much air you can breathe in and out of your lungs

●How fast you can breathe the air out of your lungs

Your doctor might order spirometry or other breathing tests to:

●Find the cause of symptoms such as a long-term cough, noisy breathing (wheezing), or trouble breathing

●Monitor a known lung condition – Breathing tests can help doctors tell if a condition is mild or severe, or has changed over time. Examples include:

•Asthma

•Weakness of the muscles used to breathe

•Interstitial lung diseases, including pulmonary fibrosis

•Chronic obstructive pulmonary disease, or "COPD"

●Check how well your inhaler medicines are working

●Check how well your lungs are working before you have surgery

Spirometry results will include 3 numbers:

●"Forced vital capacity," or "FVC" – This is the largest amount of air you can blow out after taking a deep breath.

●"Forced expiratory volume in 1 second," or "FEV1" – This is how much air you can blow out in 1 second.

●"FEV1/FVC" – This number is a fraction or percent based on the above 2 numbers. It shows how much of the FVC (total amount of air you can blow out) you blow out in 1 second.

Lower numbers might mean that you have a problem affecting your breathing.

How do I prepare for spirometry? — The doctor or nurse will tell you if you need to do anything special to prepare. If you use an inhaler, they might tell you to avoid using it for a certain amount of time before the test. They might also ask you to bring your inhaler with you.

Your doctor will also ask you about your "health history." This involves asking you questions about any health problems you have or had in the past, past surgeries, and any medicines you take.

You should also:

●Wear comfortable, loose clothing that allows you to breathe deeply.

●Avoid eating a large meal before the test.

●Do not smoke, drink alcohol, or exercise for at least 4 to 6 hours before the test.

What happens during spirometry? — When it is time for the test (figure 1):

●In most cases, you will be seated for the test.

●A clip might be placed on your nose to close your nostrils.

●You will take a deep breath in, then breathe out as hard as you can into a tube. Close your lips tightly around the tube, so no air escapes.

●As you blow out, a machine records the results of the test. You need to blow into the tube a few times so the results can be compared.

●In some cases, you might take a medicine, such as an inhaler, and then do the test again. This to see if the medicine helps your lungs.

Spirometry usually takes about 10 to 15 minutes. Your doctor or nurse might have you do other breathing tests, too.

What do my results mean? — Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

If your spirometry shows any abnormal results, your doctor or nurse will talk to you about what to do next. You might need to do other tests.

What are the risks of spirometry? — Spirometry is generally safe. But for some people, it might be uncomfortable. For example:

●It might make you cough, or feel dizzy and lightheaded.

●You might feel pressure in your chest, belly, or head.

Rarely, spirometry might cause a serious breathing problem. If this happens, the staff will help you.

Spirometry should not be done if you recently had a heart attack or have other heart problems.

More on this topic

Patient education: Breathing tests (The Basics)
Patient education: Asthma in adults (The Basics)
Patient education: Asthma in children (The Basics)
Patient education: Interstitial lung disease (The Basics)
Patient education: Idiopathic pulmonary fibrosis (The Basics)
Patient education: Chronic obstructive pulmonary disease (COPD) (The Basics)
Patient education: Cough in adults (The Basics)
Patient education: Cough in children (The Basics)
Patient education: Shortness of breath (The Basics)

Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)
Patient education: Asthma treatment in children (Beyond the Basics)
Patient education: Chronic obstructive pulmonary disease (COPD) (Beyond the Basics)
Patient education: Chronic cough in adults (Beyond the Basics)
Patient education: Shortness of breath (dyspnea) (Beyond the Basics)