Pulmonary function tests (PFTs) measure how well the lungs work by testing how much air a person can breathe in and out, as well as the lungs' ability to bring oxygen to the body. PFTs can help diagnose several respiratory conditions and diseases. Before the tests, patients should avoid medications, large meals, caffeine, smoking, and strenuous exercise. During the tests, patients breathe into a machine to test lung volume and capacity through spirometry, plethysmography, and diffusion capacity tests.

1. PULMONARY
FUNCTION TEST
(PFT)
BY,
M S . E K TA S PAT E L .

2. WHAT ARE PULMONARY FUNCTION
TESTS (PFTS)?
• Pulmonary function tests (PFTs) are a group of tests
that measure how well lungs work.
• This includes how well a person able to breathe and
how effective lungs are able to bring oxygen to the
rest of your body.
• PFTs are also known as lung function tests.

3. WHY ARE THESE TESTS DONE?
PFTs can help diagnose:
• asthma
• allergies
• chronic bronchitis
• respiratory infections
• lung fibrosis
• Bronchiectasis, a condition in which the airways in the
lungs stretch and widen

4. • COPD,
• Asbestosis, a condition caused by exposure to asbestos
• sarcoidosis, an inflammation of lungs, liver, lymph nodes, eyes,
skin, or other tissues
• scleroderma, a disease that affects your connective tissue
• pulmonary tumor
• lung cancer
• weaknesses of the chest wall muscles

5. PATIENT PREPARATION FOR PULMONARY
FUNCTION TESTS
• Avoid bronchodilators and analgesics medication
before procedure.

6. • 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 be more open which
could affect the results of your test.
• You should also avoid smoking at least an hour before
the test, as well as strenuous exercise before the test.

7. • 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 test.
• If you have had recent eye, chest, or abdominal surgery
or a recent heart attack, you will likely need to delay
testTrusted Source until you have fully recovered.

8. WHAT HAPPENS DURING THE TESTS?
• Spirometry
• 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
into the machine.
• You’ll also wear a nose clip to keep you from breathing air out through your
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 also ask you to breathe in a medication that opens your airways.
You’ll then breathe into the machine again to see if the medication affected
lung function.

9. • Plethysmography test
• A plethysmography test measures the volume of gas
in lungs, known as lung volume.
• For this test, sit or stand in a small booth and breathe
breathe into a mouthpiece.
• Your doctor can learn about your lung volume by
measuring the pressure in the booth.

10. • Diffusion capacity test
• This test evaluates how well the small air sacks inside the lungs,
lungs, called alveoli, work.
• For this part of a pulmonary function test, you will be asked to
breathe in certain gases such as oxygen, helium, or carbon
dioxide.
• 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 lungs are able to transfer oxygen and carbon dioxide
to and from your bloodstream.