Lung Function Tests: Results
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Results
Lung function tests (also called pulmonary function tests, or PFTs) evaluate 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.
Normal
Test results are within the normal ranges for a person with healthy lungs.
Abnormal
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.
Obstructive
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 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) | Lower |
FEV1 divided by FVC | Lower |
Forced expiratory flow 25% to 75% | Lower |
Lower | |
Maximum voluntary ventilation (MVV) | Lower |
Slow vital capacity (SVC) | Normal or lower |
Normal or higher | |
Functional residual capacity (FRC) | Higher |
Higher | |
Expiratory reserve volume (ERV) | Normal or lower |
RV divided by TLC ratio | Higher |
FEV1 often increases after using medicine that expands the airways in people with reversible obstructive disease like asthma.
Restrictive
In restrictive lung conditions, there is a loss of lung tissue, a decrease in the lungs' ability to expand, or a decrease in the lungs' ability to transfer oxygen to the blood (or carbon dioxide out of the blood). Restrictive lung disease can be caused by conditions such as pneumonia, lung cancer, scleroderma, pulmonary fibrosis, sarcoidosis, or multiple sclerosis. Other restrictive conditions include some chest injuries, being very overweight (obesity), pregnancy, and loss of lung tissue due to surgery.
| Lung function test | Result as predicted for age, height, sex, weight, or race |
|---|---|
Forced vital capacity (FVC) | Lower than predicted value |
Forced expiratory volume (FEV1) | Normal or lower |
FEV1 divided by FVC | Normal or higher |
Forced expiratory flow 25% to 75% | Normal or lower |
Normal or lower | |
Maximum voluntary ventilation (MVV) | Normal or lower |
Slow vital capacity (SVC) | Lower |
Lower | |
Functional residual capacity (FRC) | Normal or lower |
Normal, lower, or higher | |
Expiratory reserve volume (ERV) | Normal or lower |
RV divided by TLC ratio | Normal or higher |
| Last updated: | July 03, 2007 |
|---|---|
| Author: | Maria G. Essig, MS, ELS |
| Reviewed By: | Caroline S. Rhoads, MD - Internal Medicine, Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology |
| Editors: | Sydney Youngerman-Cole, RN, BSN, RNC, Tracy Landauer |
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