What is spirometry?

LYL Spirometry test

Spirometry measures the amount of air you can breathe out from your lungs and how fast you can blow it out. You’ll be asked to take a very deep breath and blow out as fast as you can into a mouthpiece, until no more air comes out.

A spirometry test typically takes 10 to 20 minutes, but may be longer if it includes bronchodilator responsiveness testing.

Types of spirometer

There are various different spirometer devices, but they all measure the same thing.

Many GP surgeries now have small, portable spirometers.

Some spirometers are more sophisticated and can give more detailed results. These are used in a hospital or clinic.

Man breathing into a sophisticated spirometer

Breathing into a sophisticated spirometer

What is bronchodilator responsiveness testing?

Bronchodilator responsiveness testing is done to see if your lung function gets better with medication, and if so, by how much. It’s sometimes called reversibility testing. In bronchodilator responsiveness testing, the spirometry test is done before and after you breathe in some medication.

What’s spirometry used for?

Spirometry can help tell if your breathing is affected by narrowed or inflamed airways. The results are useful in diagnosing lung conditions such as COPD and asthma. For some conditions, it can be used to grade how severe your condition is.

How should I prepare for a spirometry test?

You’ll be told if there are any particular things you need to do to prepare. You may need to stop taking bronchodilator medication before the test. You should also stop smoking for 24 hours beforehand, if you can.

On the day of your spirometry test, it’s a good idea to wear loose, comfortable clothing.

Am I fit to do the test?

Spirometry is usually safe, but there are some conditions where it may cause problems. Tell your healthcare professional if any of these apply to you:

angina

heart problems

recent 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

They will often have a checklist to ask you about these. If in doubt, talk to your health care professional.

What happens during the test?

You will be asked some questions before you start, to check you are medically fit to do the test. It is important to put as much effort into the test as you can, so the results are accurate.

You’ll be asked to sit comfortably and may have a clip put on your nose to make sure all the air goes into the mouthpiece. You will be shown how to blow into the spirometer before starting. You may be asked to blow 3 or more times into the spirometer, to check the readings are similar each time.

Normally, you will first be asked to breathe in deeply and out gently. Once your health care professional is happy with the results, you will move on to the next part of the test. You will have to breathe in again deeply, this time quite fast, and then breathe out as fast and as hard as you can until your lungs are empty.

Your health care professional may ask you to use your inhaler or other medication, wait 15–20 minutes and then repeat the test. For some drugs the wait may be 45 minutes between tests. This is called a bronchodilator responsiveness test or reversibility test and it’s done to see if the medication improves your breathing. If you use inhalers, you should bring them to your appointment.

Occasionally, people feel a little light-headed and dizzy following the test. This usually lasts only a few moments. Let the person performing the test know, to make sure that you have time to recover.

What will the results look like?

Spirometry usually measures:

how much air you can blow out in a relaxed manner, like a gentle sigh out, until your lungs are completely empty. This is called your slow vital capacity or VC

the amount of air you can blow out in one second. With healthy lungs and airways, you can normally blow out most of the air from your lungs in one second. This is called your forced expiratory volume in one second, or FEV1

the total amount of air you can blow out in one complete breath after taking a deep breath in. You will be asked to blow out as hard and as fast as you can until your lungs are completely empty. This is called your forced vital capacity or FVC

Your health care professional will look at how much air you can blow out in the first second (FEV1) and compare this to the total amount (FVC). This will give a percentage of air you can blow out in the first second.

Your results will look different depending on the type of spirometer used. Normally, your health care professional will compare your measurements with the normal range of values. The curves drawn by the spirometer showing the pattern of airflow are also important to help understand your results.