FVC: What Does My Forced Vital Capacity (FVC) Score Mean?

One of the benefits of having a spirometry test is that it can detect abnormalities in lung function even if signs and symptoms are not yet present. Not only will a spirometry test help your doctor diagnose COPD and other lung diseases in their earliest stages, it can also help your doctor determine how much damage has been done within your lungs.[1]

Four important measurements that are obtained during a spirometry test are: 1

  1. Forced vital capacity (FVC) – to recount, FVC reflects the total amount of air you can forcibly exhale after the deepest inhalation possible. Because FVC is normal or decreased in both obstructive and restrictive lung diseases, FVC alone cannot be used to diagnose lung disease. You must consider other measurements, particularly TLC (see below).
  2. Forced expiratory volume in one second (FEV1) – the amount of air that can be exhaled in one second following a deep inhalation. If this measurement is less than or equal to 69%, an obstructive lung disorder should be suspected. In restrictive disorders, this measurement is normal or minimally decreased.
  3. FEV1/FVC ratio – represents the percentage of FVC that can be exhaled in one second. People with healthy lungs generally expel 75-85% of their FVC in the first second of the test. This measurement is decreased in obstructive lung disorders and normal to minimally decreased in restrictive lung diseases.
  4. Total lung capacity (TLC) – reflects the amount of air present in the lungs after taking the deepest, fullest breath possible. TLC is normal or increased in obstructive lung disorders and decreased in restrictive lung defects.

The following chart may help you better understand these concepts:

Measurement Obstructive Pattern Restrictive Pattern
Forced vital capacity (FVC) Decreased or normal Decreased
Forced expiratory volume in one second (FEV1) Decreased Decreased
FEV1/FVC ratio Decreased Normal or increased
Total lung capacity (TLC) Normal or increased Decreased

Determining the Severity of the Abnormality

Once your doctor determines whether your lung disorder is obstructive or restrictive, she should grade the severity of the abnormality based on the FEV1 percentage of predicted. This will help your doctor choose appropriate treatment options. Although there are others equally as accurate, the following chart represents the American Thoracic Society’s system for determining the severity of lung disease:[2]

American Thoracic Society Grading System for Pulmonary Function Test Abnormality 
Severity of Lung Disease FEV1 Percentage of Predicted 
Mild > 70
Moderate 60-69
Moderately severe 50-59
Severe 35-49
Very severe < 35

Bronchodilator Reversibility

If your spirometry results indicate an obstructive defect, your doctor may administer a bronchodilator challenge to determine if the obstruction is reversible. It’s considered reversible if the FEV1 or the forced vital capacity (FVC) increase by more than 12% and 200 milliliters in adults 18 years of age and older. Please note: obstruction is usually fully reversible in asthma whereas it may be only partially reversible in people with COPD.

For more information about forced vital capacity and other pulmonary function test measurements, talk to your pulmonologist or primary care provider.

[1] Johnson, Jeremy D., MD, MPH & Theurer, Wesley M., DO, MPH. A Stepwise Approach to the Interpretation of Pulmonary Function Test. Am Fam Physician. 2014 Mar 1;89(5):359-366.

[2] American Thoracic Society. Gading System for Pulmonary Function Test Abnormality. Accessed March 17, 2017.


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