What Is Spirometry?

When you’re having trouble breathing, your doctor might order a test called spirometry. It’s a very common test used to understand how well your lungs work. Spirometry measures three things:

  1. How much air you can breathe in
  2. How much air you can breathe out
  3. How fast you can exhale the air from your lungs

Based on those measurements, your doctor can start to diagnose problems such as COPD (chronic obstructive pulmonary disease), asthma, and certain other conditions that make breathing difficult.

Preparing for the Test

You don’t need to do anything to prepare for spirometry, though there are a few things to keep in mind:

  • You should avoid a big meal right before the test.
  • Check with the doctor to see whether there are medications you should not take the day of the test.
  • Wear comfortable clothes.

The test itself takes about 15 minutes. It’s done in your doctor’s office and afterwards, you can go about your day as normal.

How It Works

You’ll sit in a chair and have a clip placed on your nose to keep your nostrils closed. Then you’ll take a deep breath and exhale as quickly and hard as you can into a tube.

You’ll need to wrap your lips tightly around the tube so all your air goes into it. Usually, the test is given 3 times to make sure the results are consistent.

The tube is connected to a machine called a spirometer. It records how much air is exhaled from your lungs. The speed at which you can exhale is also recorded.

All this information helps the doctor diagnose a lung disease if you have one.

Any Downside to This Test?

Spirometry is a painless test. Most people have no problems with it. Depending on your health, you may feel a little lightheaded or tired after the test and all that inhaling and exhaling.

If you have heart disease or have had a recent surgery, you should check with your doctor to make sure spirometry won’t be a problem for you.


Results and Diagnosis

You might hear your doctor or a technician refer to two key measurements in spirometry. They are:

  • Forced vital capacity (FVC). This measures the amount of air you can breathe in and out.
  • Forced expiratory volume (FEV-1). This measures how much air you can exhale from your lungs in 1 second.

The results are usually given to a specialist to review. Your doctor should get a report within a few days and should talk it over with you.

If your doctor suspects you have blocked airways, you may be given a medication that opens them up. It’s called a bronchodilator. After several minutes, you may take the spirometry test again to see if the bronchodilator made a difference.

A poor FEV-1 score suggests you have an “obstructive airways” disease, such as COPD. An obstructive airways disease means your lungs can fill with air normally, but your airways are too narrow to exhale properly.

If your lungs can’t fill normally, you have a “restrictive lung disease.”

There are several types of these conditions, but one of the most common is pulmonary fibrosis. If you have this disease, some of the tissue in your lungs has become hard. It won’t expand as needed when you inhale, so you can never get quite enough breath.

Do I Need Spirometry?

This is one of the most important tests in diagnosing lung disease.

If you’re having any breathing problems, it wouldn’t hurt to talk about spirometry with your doctor. If it’s possible you have COPD, asthma, or some other lung issue, this test is a good first step in diagnosing your condition.

Spirometry is also helpful in testing how well a bronchodilator or other treatment is working. You may have had spirometry testing when you were first diagnosed with asthma. A test after you have been taking asthma medications for a while can let you and your doctor know whether you’re on the right treatment track.

WebMD Medical Reference Reviewed by Jennifer Robinson, MD on March 13, 2019



Mayo Clinic: “Spirometry: Definition,” “Spirometry: What can you expect,” “Spirometry: Why it’s done.”

National Health Service: “Spirometry.”

Lung Institute: “What is pulmonary fibrosis?”

Asthma and Respiratory Foundation of New Zealand: “What is Spirometry?”

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