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What is a pulmonary function test?

Pulmonary function tests (sometimes called lung function tests) measures how well your lungs are working. There are various different tests which all involve blowing into various analytical equipment to measure values such as airflow and lung volume. Such tests are often requested by respiratory or other specialists for people who are short of breath, or have found that they are unable to exercise for reasons which are unclear, but are though to relate to the lungs.

Is pulmonary function test right for me?

Pulmonary function test is a key investigation for anyone with shortness of breath, particularly if the symptoms have developed over a period of weeks or longer - an emergency visit to your GP or hospital would be more appropriate for shortness of breath which has developed over hours or days.

Shortness of breath may be due to any number of different pulmonary conditions including asthma, long COVID, COPD or pulmonary fibrosis (scarring), to name just a few. Pulmonary function testing may also be required in some cases prior to undergoing surgery, to determine fitness for anaesthesia.

What happens during pulmonary function testing?

Preparing for pulmonary function testing

We often advise people to omit any inhaled therapy you are using for a day or so prior to testing. This helps to obtain a truer impression of how healthy your lungs are. You will be given instructions in this regard.

It is preferable to avoid a large meal or fizzy drinks immediately prior to testing. It's also better to avoid any tight-fitting clothing, which may restrict the movement of your chest or abdomen.

Lung function testing is usually avoided for a few weeks after surgery and there are certain medical conditions which may be a bar to testing, if felt to be unstable.

During pulmonary function testing

The testing is performed with the subject seated in a glass cabinet. The door may be left open for most of the tests for those who are anxious in this environment.

For each of the tests, the subject is asked to breathe in and out of a mouthpiece, whilst various measurements are made. These may include lung volume, airflow, airway resistance and the efficiency of your lungs in transferring oxygen to the circulation.

Typically, this may take 30-40 minutes. An interpretation of the findings is included with the results.


Some people find the tests a little tiring, but no specific recovery or time off are required after testing.

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