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Lung Disease & Respiratory Health Center

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Lung Function Tests

How It Feels

If you have an arterial blood gas test, you may feel some pain from the needle used to collect the blood. The other lung function tests are usually painless. Some of the tests may be tiring for people who have a lung disease.

You may cough or feel lightheaded after breathing in or out rapidly, but you will be given a chance to rest between tests. You may find it uncomfortable to wear the nose clip. Breathing through the mouthpiece for a long period of time may be uncomfortable.

If you have body plethysmography, you may feel uncomfortable in the airtight plethysmograph booth. But the therapist will be nearby during the test to open the door if you feel too uncomfortable.

If you are given breathing medicine, it may cause you to shake or may increase your heart rate. If you feel any chest pain or discomfort, tell the therapist right away.


Lung function tests present little or no risk to a healthy person. If you have a serious heart or lung condition, discuss your risks with your doctor.


Lung function tests (also called pulmonary function tests, or PFTs) check how well your lungs work. The normal value ranges for lung function tests will be adjusted for your age, height, sex, and sometimes weight and race. Results are often expressed in terms of a percentage of the expected value. Most test results are available right away.


Test results are within the normal ranges for a person with healthy lungs.


Test results are outside of the normal range for a person with healthy lungs. This may mean that some kind of lung disease is present. There are two main types of lung disease that can be found with lung function tests: obstructive and restrictive.


In obstructive lung conditions, the airways are narrowed, usually causing an increase in the time it takes to empty the lungs. Obstructive lung disease can be caused by conditions such as emphysema, bronchitis, infection (which produces inflammation), and asthma.

Lung function values in obstructive disease
Lung function test Result as predicted for age, height, sex, weight, or race

Forced vital capacity (FVC)

Normal or lower than predicted value

Forced expiratory volume (FEV1)


FEV1 divided by FVC


Forced expiratory flow 25% to 75%


Peak expiratory flow (PEF)


Maximum voluntary ventilation (MVV)


Slow vital capacity (SVC)

Normal or lower

Total lung capacity (TLC) (VT)

Normal or higher

Functional residual capacity (FRC)


Residual volume (RV)


Expiratory reserve volume (ERV)

Normal or lower

RV divided by TLC ratio


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

WebMD Medical Reference from Healthwise

Last Updated: /2, 14 1
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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