Definition of Forced Vital Capacity or FVC

FVC as a First Step in Evaluating Lung Disease

spirometer Photo©dina2001

Forced vital capacity, or FVC, is the amount of air which can be forcibly exhaled from the lungs after taking the deepest breath possible. FVC is used to help determine both the presence and severity of lung diseases.

Measuring Forced Vital Capacity (FVC)

Forced vital capacity (FVC) is measured in a test known as spirometry, a type of pulmonary function test.  In spirometry testing, a mask is placed over your face.

  Measurements are taken as you breathe in and then breathe out (exhale) as forcefully as possible.

Reasons to Measure Forced Vital Capacity (FVC)

There are many reasons for which your doctor may choose to measure your FVC - the amount of air you can forcefully exhale. These may include:

  • To evaluate symptoms that could indicate lung diseases, such as shortness of breath, coughing, or wheezing.
  • To monitor lung diseases already diagnosed to see if they are getting worse, or see if they are improving at all with treatment.
  • To evaluate your ability to tolerate surgery or an exercise program.  Sometimes surgeons want to make sure your breathing is stable prior to surgery, especially if you will be having lung surgery.  In addition, some people have this test done before embarking on a new exercise program.
  • Assessing heart disease risk.  In recent years, it's been found that FVC is correlated inversely with the risk of developing heart disease, even when it is still in the "normal" range.
  • As an endpoint in clinical trials.  Clinical trials looking to assess how well a medication is working may measure FVC in large numbers of people to compare with conventional treatments.

What the Test Really Measures

In measuring the amount of air you can forcefully blow out, doctors can determine several things about your lungs function.

  Doctors first compare your measurement to what would be predicted based on your age, your height, and your weight. 

Obstructive vs Restrictive Lung Disease - FEV1/FVC

Since FVC can be decreased similarly in both obstructive and restrictive lung diseases, it is often most helpful when used as a ratio with the amount of air which can be forcefully exhaled in 1 second. In other words, the ratio of FEV1/FVC helps to differentiate obstructive from restrictive lung disease. When FEV1 makes up less than 80% of FVC it indicates that obstruction is going on in the lungs. The obstruction can be either reversible, as with asthma, or irreversible, as with COPD. In restrictive lung diseases, such as pulmonary fibrosis, both numbers are decreased proportionally.

Conditions Associated with a Decreased FVC

It's important to note that FVC can be looked at in 2 ways.  Both a comparison with what your FVC is predicted to be based on your age, height, and weight, and how your FVC changes personally for you over time.

  FVC can be decreased in a number of different conditions, and may be temporary or permanent.  Some of these include:

  • Chronic obstructive pulmonary disease (COPD) - Including chronic bronchitis (FVC may be normal or decreased) emphysema (FVC is decreased) and bronchiectasis.
  • Restrictive airway diseases such as idiopathic pulmonary fibrosis.
  • Structural restrictive airway disease such as that produced by scoliosis and chest scarring.
  • Diseases such as sarcoidosis.
  • Inflammatory lung diseases such as asbestosis and silicosis.
  • Lung cancer.

The next step if FVC is decreased is to check the ratio FEV1/FVC to separate out lung diseases into a restrictive or obstructive pattern.  If the ratio is equivalent, this represents a restrictive lung disease and full pulmonary function tests will likely be needed.  If the ratio is less than 80% (plus or minus depending on age and other factors) the lung disease would be characterized as obstructive.  The first step then would be to see if the obstruction is reversible (with a bronchodilator) or not.

Effects of Smoking on Forced Vital Capacity (FVC)

Cigarette smoking, in addition to all of its other dangers, decreases FVC.  The alarming thing recently for physicians is how quickly this occurs - even in teenagers who have just recently taken up the habit.


Johnson, J., and W. Theurer. A Stepwise Approach to the Interpretation of Pulmonary Function Tests. American Family Physician. 2014. 89(5):359-366.

Godfrey, M., and M. Jankowich. The Vital Capacity Is Vital:Epidemiology and Clinical Significance of the Restrictive Spirometry Pattern. Chest. 2016. 149(1):238-251.

Koo, K., Yun, H., Byeong-Ho, J. et al. Relationship Between Forced Vital Capacity and Framingham Cardiovascular Risk Score Beyond the Presence of Metabolic Syndrome: The Fourth Korea National Health and Nutrition Examination Survey. Medicine. 2015. 94(47):e2089.

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