Are Pulmonary Function Tests (PFTs)?
Pulmonary function tests (PFTs)
are a group of tests that measure how well your lungs work. This includes how
well you’re able to breathe and how effective your lungs are able to bring
oxygen to the rest of your body.
Your doctor may order these tests:
- if you’re having symptoms of lung problems
- as part of a routine physical
- to monitor how effective your treatment is if
you have a lung disease, such as asthma
- to assess how well your lungs are working before
you have surgery
PFTs are also known as spirometry or lung function tests.
Are These Tests Done?
Your doctor will order these tests to determine how your lungs
are working. If you already have a condition that’s affecting your lungs, your
doctor may order this test to see if the condition is progressing or how it’s
responding to treatment.
PFTs can help diagnose:
- chronic bronchitis
- respiratory infections
- lung fibrosis
- bronchiectasis, which is a condition in which
the airways in the lungs stretch and widen
- chronic obstructive pulmonary disease (COPD), which
used to be called “emphysema”
- asbestosis, which is a condition caused by
exposure to asbestos
- sarcoidosis, which is an inflammation of your
lungs, liver, lymph nodes, eyes, skin, or other tissues
- scleroderma, which is a disease that affects
your connective tissue
- pulmonary tumor
- lung cancer
Do I Prepare for Pulmonary Function Tests?
If you’re on medications that open your airways, such as those
used for asthma or bronchitis, your doctor may ask you to stop taking them
before the test. If it isn’t clear whether or not you should take your
medication, make sure to ask your doctor. Pain medications may also affect the
results of the test. You should tell your doctor about any over-the-counter and
prescription pain medications you’re taking.
It’s important that you don’t eat a large meal before testing. A
full stomach can prevent your lungs from inhaling fully. You should also avoid
food and drinks that contain caffeine, such as chocolate, coffee, and tea,
before your test. Caffeine can cause your airways to open. You should also avoid
smoking and strenuous exercise before the test.
Be sure to wear loose-fitting clothing to the test. Tighter
clothing may restrict your breathing. You should also avoid wearing jewelry
that might affect your breathing. If you wear dentures, wear them to the test
to ensure that your mouth can fit tightly around the mouthpiece used for the
Happens During the Tests?
Your PFTs may include spirometry, which measures the amount of
air you breathe in and out. For this test, you’ll sit in front of a machine and
be fitted with a mouthpiece. It’s important that the mouthpiece fits snugly so
that all the air you breathe goes into the machine. You’ll also wear a nose
clip to keep you from breathing air out through your nose. The respiratory
technologist will explain how to breathe for the test.
You may then breathe normally. Your doctor will ask you to breathe
in and out as deeply or as quickly as you can for several seconds. They may ask
you to breathe in a medication that opens your airways or breathe in certain
gases such as oxygen, helium, or carbon dioxide. You’ll then breathe into the
machine again to see if the medication or gases affected your lung function.
You may also breathe in a “tracer gas” for one breath. The
machine can detect when you breathe out this gas. This tests how well your
lungs are able to transfer oxygen and carbon dioxide to and from your
A plethysmography test measures the volume of gas in your lungs.
For this test, you’ll sit or stand in a small booth and breathe into a
mouthpiece. Your doctor can learn about your lung volume by measuring the
pressure in the booth.
Are the Risks of Taking Pulmonary Function Tests?
A PFT can cause problems if:
- you’ve recently had a heart attack
- you’ve had recent eye surgery
- you’ve had recent chest surgery
- you’ve had recent abdominal surgery
- you have a severe respiratory infection
- you have heart disease
PFTs are usually safe for most people. However, because the test
may require you to breathe in and out quickly, you may feel dizzy and there’s a
risk that you might faint. If you feel lightheaded, tell your doctor. The test
may cause you to have an asthma attack if you have asthma. In very rare cases, PFTs
may cause a collapsed lung.