Pulmonary function tests (PFTs) measure how well your lungs take in and exhale air and how efficiently they transfer oxygen into the blood. There are several different tests:
Pulmonary function tests help:
PFTs can help find lung disease at an early stage, before you have symptoms. If your lungs are damaged, these tests can sometimes estimate the amount of lung damage. They can also help see if your breathing problems are reversible and likely to get better after using a medicine that opens up the airways.
Eat a light meal and do not smoke for 4 to 6 hours before your test. If you have asthma, ask your healthcare provider if you need to stop using asthma medicine before the test.
Sometimes, you will be asked to do this test before and after using an inhaled medicine. The medicine is called a bronchodilator. It helps open up small airways.
PFTs are not painful, and you will have time to rest between the different breathing tests. The tests may be repeated 2 or more times.
Ask your healthcare provider when and how you will get the results of your tests.
If you do not have lung disease, you will be able to blow out 80% or more of the air in your lungs in 1 second. If you have lung disease, it may take you longer to get all of the air out of your lungs. For example, you may be able to blow out only 20% to 40% of the air in your lungs in 1 second.
PFTs may show what type of lung disease you have.
A low diffusion capacity may be a sign of emphysema. It may also be caused by a restrictive lung disease that thickens the lung membrane.
Test results are only one part of a larger picture that takes into account your medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your healthcare provider about your results and ask questions.
If your test results are not normal, ask your healthcare provider: