Spirometry and bronchodilator reversibility test

Find out about spirometry, when the test is used with a bronchodilator reversibility test, what happens during the tests, and what your results might show

What is spirometry?

Spirometry is a breathing or lung function test. It measures how much air you can breathe out in one forced breath.  

You may do a spirometry test at the GP surgery, or you may be given a short appointment at a clinic or hospital outpatients department.

Who can have a spirometry test?

Spirometry is suitable for most adults, young people, and children over five.  

But because a spirometry test increases pressure in your head, chest, stomach and eyes, it may not be suitable for you if you have, or have recently had:

  • angina
  • heart problems
  • concussion
  • uncontrolled high or low blood pressure
  • pulmonary hypertension
  • pulmonary embolism
  • pneumothorax
  • recent surgery on the brain, middle ear, sinuses, eyes, chest or abdomen
  • late-term pregnancy
  • aneurysms.

When is spirometry used?

Spirometry is used to diagnose and monitor some lung conditions.

Spirometry to help diagnose lung conditions

Spirometry is used to help diagnose asthma and chronic obstructive pulmonary disease (COPD). 

It can also help identify other lung issues, such as pulmonary fibrosis (scarring in the lungs). 

Spirometry to help monitor lung conditions

Spirometry can be used to monitor your lung condition, especially if it’s not well controlled.

It can help check how you’re responding to treatment.

If you have asthma, your GP or asthma nurse may suggest a spirometry test at your annual asthma review. 

How is a spirometry test done?


A spirometry test is done using a small machine attached to a mouthpiece, called a spirometer.  
The nurse or healthcare assistant can show you how to blow into the spirometer before starting the test.
To do the test you need to:

  • Sit comfortably
  • Wear a clip on your nose to make sure all the air from your lungs goes into the mouthpiece.
  • First do a relaxed breath - it is often described as a big sigh into the machine.
  • Then take a deep breath and breathe out as fast and as hard as you can, for as long as you can, through the mouthpiece.

You will need to blow a few times, and put as much effort into the test as you can, to get an accurate result.

"Spirometry is a safe, easy test to do,” says Dr Andy Whittamore, Asthma + Lung UK’s clinical lead.

“Some people can feel a bit dizzy or faint afterwards, but this usually lasts just a few minutes.  If you do feel a bit faint or lightheaded afterwards, let the person performing the test know, to make sure that you have time to recover.”

How is spirometry used with a bronchodilator reversibility test?

A spirometry test is often done alongside a bronchodilator reversibility test (BDR).

The two tests together can show if your airways open up with bronchodilator medicines, and if so, by how much.  
Spirometry used with a BDR test can show:

  •  if symptoms might be caused by asthma, (COPD), or Asthma-COPD overlap (ACO). ACO is where people have features of both asthma and COPD. If your airways open up well after taking reliever medicine through a spacer, it makes it more likely that you have asthma or COPD. 
  • how well your medicines are working, particularly if your treatment plan has changed 

Bronchodilator medicines

Bronchodilator medicines relax the muscles in the lungs and open the airways. This makes breathing easier.

A reliever inhaler contains bronchodilator medicine to help with asthma attacks and flare ups.

How is a bronchodilator reversibility test done?

If the spirometry test shows that your airways are narrowed, you may need to do a BDR test.   This is when you do a second spirometry test after taking bronchodilator medicine.
This is so your healthcare professional can check how your airways respond to the bronchodilator medicine.

  1. First you do a spirometry test. Your healthcare professional will take note of the results.
  2. Then you use your reliever inhaler or other bronchodilator medicines.
  3. You wait 15-20 minutes and then do another spirometry test.

If you use inhalers, you should bring them, and your spacer if you have one, to your appointment.

What do my spirometry and BDR test results show?

You won’t get your results straight away. They will need to be looked at by a specialist first. Your healthcare professional will then talk through the test results with you.

The test shows if your airways are obstructive, restrictive, or a combination of the two.

Obstructive airway result

An obstructive result can mean you have a lung condition that narrows your airways, such as COPD or asthma. This shows that the amount of air you can hold in your lungs is normal, but the air flows out of your lungs more slowly than it should.

Spirometry doesn’t measure how inflamed your airways are. But if the results show your airways are obstructed, it could be due to inflammation.

Doing spirometry again after taking the reliever medicine (the bronchodilator reversibility test) may give a different test result . The result can show if your airways have responded to the medicine.

Reliever medication usually changes the results more if you have asthma, rather than COPD. 

Restrictive airway result

A restrictive result shows that the total amount of air you can breathe in is reduced because your lungs cannot fully expand.

This might be because of conditions that affect the tissue in your lungs, such as pulmonary fibrosis.

 If your results show a restrictive pattern, you may also have a lung volume test to check if you have a low lung volume .

Combination of obstructive and restrictive

Some people may have a mix of obstructive and restrictive results using spirometry. This happens when both the total amount of air, and how fast you can blow out, are reduced.

Your healthcare professional will compare your results to measurements that are normal for someone of your age, height, weight, ethnicity and sex.

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