Pulmonary function tests (PFTs) are a group of breathing tests. They can show how well your lungs are working. PFTs may measure:
- How much air you can blow out
- How much air your lungs can hold at different times during the breathing cycle
- How fast you are blowing air out
- How well gas is being transferred from your lungs into your blood
Reasons for Test
PFTs may be used to help diagnose lung conditions or diseases, such as:
- Chronic bronchitis
- Cystic fibrosis
- Alpha-1 antitrypsin deficiency
- Idiopathic pulmonary fibrosis
- Interstitial lung disease
These tests may also be done to:
- Determine how well a treatment is working
- Evaluate symptoms, such as coughing, wheezing, and trouble breathing
- Evaluate your lung function before or after a surgery
- Measure how much a lung problem or muscle weakness is affecting you
What to Expect
Prior to Test
- Review your medications with your doctor. You may need to stop taking some before testing.
- Do not eat, smoke, or exercise 4-8 hours before testing.
- Wear loose-fitting clothing.
Description of Test
Most tests will require you to breathe into a mouthpiece. The mouthpiece may be attached to a simple handheld device or be part of a larger machine. Examples of devices are a spirometer or peak flow meter. You may be asked to breathe in and out in different patterns and speeds. You will rest between tests.
Tell the technician right away if you have breathing problems, pain, or dizziness during testing.
Other tests that may be used in some situations include:
- A brief period of exercise before the test.
- Oxygen saturation test to measure the amount of oxygen in the blood. Can be measured with a small clip on your finger.
- You may be exposed to a specific chemical called methacholine during the PFT. The test will determine if your breathing changes due to that chemical. This is only done under close and careful supervision.
You may be asked to breathe in small amount of carbon monoxide for 1 minute to find out how much gets into your blood. This indicates how well oxygen is getting into your blood.
Rest until you feel able to leave. You may be given medication if testing has caused wheezing, coughing, and/or difficulty breathing.
How Long Will It Take?
Will It Hurt?
The test does not hurt. You may feel symptoms of your lung condition during or immediately following testing.
Your doctor will compare the results of your tests with normal values based on your age, gender, and height, or previous test results. Your doctor will discuss the results with you and decide if further testing or treatment is needed.
Call Your Doctor
After the test, call your doctor if any of the following occurs:
- Headaches, nausea, muscle aches, lightheadedness, or general ill feeling
- Shortness of breath or difficulty breathing
- Wheezing or persistent coughing
- Chest pain
- Reviewer: EBSCO Medical Review Board Michael Woods, MD, FAAP
- Review Date: 09/2017 -
- Update Date: 08/29/2017 -