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Lung Function Tests

Lung function tests (also called pulmonary function tests, or PFTs) check how well your lungs work. The tests determine how much air your lungs camera.gif can hold, how quickly you can move air in and out of your lungs, and how well your lungs put oxygen into and remove carbon dioxide from your blood. The tests can diagnose lung diseases, measure the severity of lung problems, and check to see how well treatment for a lung disease is working.

Other tests—such as residual volume, gas diffusion tests, body plethysmography, inhalation challenge tests, and exercise stress tests—may also be done to determine lung function.

Spirometry

Spirometry is the first and most commonly done lung function test. It measures how much and how quickly you can move air out of your lungs. For this test, you breathe into a mouthpiece attached to a recording device (spirometer). The information collected by the spirometer may be printed out on a chart called a spirogram.

The more common lung function values measured with spirometry are:

  • Forced vital capacity (FVC). This measures the amount of air you can exhale with force after you inhale as deeply as possible.
  • Forced expiratory volume (FEV). This measures the amount of air you can exhale with force in one breath. The amount of air you exhale may be measured at 1 second (FEV1), 2 seconds (FEV2), or 3 seconds (FEV3). FEV1 divided by FVC can also be determined.
  • Forced expiratory flow 25% to 75%. This measures the air flow halfway through an exhale.
  • Peak expiratory flow (PEF). This measures how much air you can exhale when you try your hardest. It is usually measured at the same time as your forced vital capacity (FVC).
  • Maximum voluntary ventilation (MVV). This measures the greatest amount of air you can breathe in and out during 1 minute.
  • Slow vital capacity (SVC). This measures the amount of air you can slowly exhale after you inhale as deeply as possible.
  • Total lung capacity (TLC). This measures the amount of air in your lungs after you inhale as deeply as possible.
  • Functional residual capacity (FRC). This measures the amount of air in your lungs at the end of a normal exhaled breath.
  • Residual volume (RV). This measures the amount of air in your lungs after you have exhaled completely. It can be done by breathing in helium or nitrogen gas and seeing how much is exhaled.
  • Expiratory reserve volume (ERV). This measures the difference between the amount of air in your lungs after a normal exhale (FRC) and the amount after you exhale with force (RV).

Gas diffusion tests

1 | 2 | 3 | 4 | 5 | 6 | 7

WebMD Medical Reference from Healthwise

Last Updated: April 25, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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