Lung Function Tests
Body plethysmography may be
used to measure:
- Total lung capacity (TLC), which is the total amount of air
your lungs can hold. For this test, you sit inside a small airtight room called
a plethysmograph booth and breathe through a mouthpiece while pressure and air
flow measurements are collected.
- Residual volume (RV), which is the
amount of air that remains in your lungs after you exhale as completely as
possible. For this test, you sit inside the plethysmograph booth and breathe
while the pressure of the booth is monitored. You may need to breathe through a
mouthpiece while you are in the booth.
Inhalation challenge tests
Inhalation challenge tests are done to measure the
response of your airways to substances that may be causing
asthma or wheezing. These tests are also called
inhalation testing, increasing amounts of a substance are inhaled through a
nebulizer, a device that uses a face mask or mouthpiece to deliver the
substance in a fine mist (aerosol). Sometimes, increasing amounts of methacholine or mannitol may be inhaled through the nebulizer. Spirometry
readings are taken to evaluate lung function before, during, and after inhaling
In rare cases, a
bronchospasm can occur with inhalation challenge
testing. You will be closely monitored during and after the test.
Exercise stress tests
Exercise stress tests
evaluate the effect of exercise on lung function tests. Spirometry readings are
done after exercise and then again at rest.
Multiple-breath washout test
washout test is done to check lung function in people with cystic fibrosis. For
this test, you breathe air that contains a tracer gas through a tube. Then you
breathe regular air while the amount of tracer gas you exhale is monitored.
Test results are reported as a lung clearance index (LCI). A high LCI value
means that the lungs are not working well.
Lung function results are measured directly in some
tests and are calculated in others. No single test can determine all of the
lung function values, so more than one type of test may be done. Some of the
tests may be repeated after you inhale medicine that enlarges your airways
Why It Is Done
Lung function tests are done to:
- Determine the cause of breathing
- Diagnose certain lung diseases, such as
chronic obstructive pulmonary disease (COPD).
- Evaluate a person's lung function before
- Check the lung function of a person who is regularly
exposed to substances such as asbestos that can damage the lungs.
- Check the effectiveness of treatment for lung diseases.
How To Prepare
Tell your doctor if you:
- Have had recent chest pains or a
- Take medicine for a lung
problem such as asthma. You may need to stop taking some medicines before
- Are allergic to any medicines.
- Have had recent
surgery on your eyes, chest, or abdomen, or if you have had a collapsed lung