What Is Spirometry?

Spirometry Test Overview

Spirometry helps doctors figure out the cause of symptoms like long-term cough.
Spirometry helps doctors figure out the cause of symptoms like long-term cough.

Spirometry is a test to see how well your lungs work. It does this by measuring how much air goes in and how much goes out as you breathe. It shows how well you can fill your lungs and how quickly you can exhale that air. The test uses a device called a spirometer.

The info that follows is meant to give you a better understanding of what the test is and how it’s used. It also explains what it might mean for you someday.

Why Would I Need Spirometry?

Spirometry helps your doctor figure out the cause of symptoms like long-term cough or shortness of breath. Along with other tests, it helps diagnose conditions such as:

If you have a lung disease, doctors can use spirometry to test changes in your lung function over time. This shows whether your condition is getting better with treatment.

Your doctor might also use spirometry to:

  • Help select treatments for your lung condition
  • Check how well inhaled medicines might work for you
  • Look for early signs of narrowing airways or lung scarring
  • See whether you’ve breathed in a harmful substance
  • Check if your lungs are strong enough to handle a surgery you may need

How Should I Prepare for a Spirometry Test?

Spirometry is a quick test in your doctor’s office or a lung clinic. Before your test, you’ll take these steps to make sure you’re comfortable during the exam and that you get accurate results:

  • Ask your doctor if there are any medicines you should skip and for how long.
  • Don’t use a short-acting inhaler for 6 to 8 hours before the test.
  • Don’t smoke for 1 hour or drink alcoholic beverages for 4 hours before your test.
  • Don’t eat a large meal for 2 hours beforehand.
  • Don’t do any vigorous activity for a half hour before the test.
  • Wear comfortable clothes that allow you to take deep breaths.

Be sure to tell your doctor if you’ve had any of the following serious health problems. She may want to cancel or delay your test until you’re better:

How Is a Spirometry Test Performed?

Spirometry only takes about a half hour to 45 minutes to complete. You’ll sit upright for the whole test.

First, the technician will place a clip on your nose. This helps you breathe through your mouth.

Then, you will clamp your lips around the plastic mouthpiece connected to the spirometer. Follow the technician’s instructions on how to breathe. You’ll inhale as deeply as you can then exhale as quickly and forcefully as you can. Use as much energy and effort as possible when you breathe in and out. That gets the most accurate results. You’ll repeat this breathing exercise at least three times.

Your technician may give you a medication called a bronchodilator. It opens your airways. About 15 minutes later, you will do the breathing test again to see if there are any changes in your results. Comparing the results before and after you take a bronchodilator will show whether this medicine helps you.

During the test, some people feel lightheaded or dizzy, cough, or feel chest tightness. If you feel uncomfortable, tell the technician.

You may also feel a little lightheaded or tired after spirometry. Some people cough a little. These effects should go away very quickly so you can get back to your normal activities.

After the test is over, you can get back on your regular medication schedule.

What Are Normal Levels for a Spirometry Test?

Spirometry results show how your lung function compares to that of someone your age, height, and sex with normal, healthy lungs. Results include these measurements:

  • FEV: Forced expiratory volume is the percentage of air you can exhale from your lungs in a forced breath. You get results for each of the three breaths you take on the test: FEV1, FEV2, and FEV3. People with normal, healthy lungs can exhale 80% or more of the air from their lungs. Lower than normal FEV means something is blocking your airways.
  • FVC: Forced vital capacity is the total amount of air you exhaled during the FEV test. A lower than normal FVC means something is restricting your breathing.

For both FVC and FEV, here’s what lower than normal scores may suggest:

  • Mild lung condition: 70% to 79%
  • Moderate lung condition: 60% to 69%
  • Severe lung disease: Less than 60%

FVC/FEV-1: Spirometry also takes these two scores and calculates your FVC/FEV-1 ratio. This tells you the percentage of your lung’s air space that you can exhale in one second. Normal results are 70% or more for adults under 65.

FVC/FEV-1 ratios below normal help your doctor rate the severity of your lung condition:

  • Mild lung condition: 60% to 69%
  • Moderate lung condition: 50% to 59%
  • Severe lung condition: Less than 50%

What Happens After You Get The Results?

Once you have your results, your doctor may prescribe treatment for your lung condition. You might need to repeat spirometry later to track how you’re doing.

Your doctor can set goals for your treatment based on ongoing spirometry results.

(c)2019 WebMD, LLC. All rights reserved.

Mayo Clinic: “Spirometry,” “Interstitial Lung Disease.”

American Lung Association: “Spirometry.”

Cleveland Clinic: “Spirometry.”

Lung Association of Canada: “Spirometry.”

American Family Physician: “An Approach to Interpreting Spirometry.”

United Steel Workers Worker Health Protection Program: “Understanding Your Breathing Test Results.”