Forced vital capacity (FVC) is the amount of air that can be forcibly exhaled from the lungs after inhaling as deeply as possible, measured by spirometry. This test can help distinguish obstructive lung diseases like asthma and COPD from restrictive lung diseases like pulmonary fibrosis and sarcoidosis .
FVC can also help healthcare providers assess lung disease progression and evaluate the effectiveness of treatment. Abnormal FVC can be chronic, but sometimes the problem is reversible and FVC can be corrected.
The purpose of the test
FVC is used to assess your lung function. Measures the effect of lung disease on your ability to breathe in and out.
While the FVC cannot determine what specific lung disease you have, the results can help narrow down possible diagnoses and can be used, along with other studies, to determine what lung disease you have.
Reasons you may need to measure FVC include:
FVC and VC record similar information: they both measure how much air you can exhale after maximizing inhalation. But FVC refers to the amount of air that you can forcefully exhale, while VC records the maximum amount of air that you exhale during normal breathing.
FEV1 is different because it measures how much air you can breathe out in one second.
Your FVC and other lung function tests (PFTs) are used to determine the status of your lung function by comparing your measurements with standards based on your age, gender, race, height, and weight.
Risks and contraindications.
FVC requires your cooperation and effort, but it is safe. However, the first time you use a spirometer , a device used to measure FVC, be sure to consult your doctor. You can potentially use the spirometer incorrectly, exhausting.
Later, they may tell you how to use it at home . You should also ensure that the spirometer you are using has been thoroughly cleaned before each use so that you are not exposed to anything that could cause an infection.
If you have a friend or family member who uses home spirometry tests, do not use your device to measure your own FVC or other lung function tests.
Before the test
Before the FVC test, your healthcare professional can give you instructions on your medications. You may also be asked to use your inhaler (or other medicine) so your healthcare team can assess how well it is working.
Lung infection or exposure to cigarette smoke can also affect your results, so it is important to discuss these issues with your healthcare provider before testing. Your FVC can be transferred if necessary.
The FVC test itself should only take a few minutes, but be sure to ask your healthcare team how long to spend at the test site.
There are other aspects of lung testing, such as functional residual capacity (FRC) , and you may need different tests if your lung condition is difficult to diagnose or if your condition does not improve as expected.
The entire battery of tests may take an hour or more.
You will have an FVC test done at your PCP's office or at a lung testing lab.
What to wear
Make sure you wear loose-fitting clothing so you don't feel restricted in breathing. It is important that you are able to inhale and exhale as much as possible during the test.
Food and drink
You will not need to make any changes to your diet before or after the FVC test.
Cost and health insurance
The price for this test can range from $ 40 to $ 80. If you have health insurance, your operator may cover all or part of this cost. Be sure to check with your insurance company if you will have to pay a copayment or the full cost of the test.
Keep in mind that if you have other lung tests, your total cost will be higher.
When you go for an FVC test, be sure to bring a list of all your medications, an identification form, your health insurance information, and a form of payment.
Take your inhalers with you, even if you have been told not to use them before the test; You may be asked to use an inhaler during the test.
During the exam
When you arrive for the test, you will be asked to log in and submit your documents. You will meet with the medical team, which may include a technician, nurse, and / or doctor.
Throughout the test
Spirometry is non-invasive and only takes a few minutes. Most likely, other lung function tests will be done at the same appointment.
FVC spirometry is performed as follows:
- You are sitting in a chair and are being asked to breathe comfortably.
- A clip is placed on the nose.
- You will be given a tube to inhale.
- By pressing your lips hard against the tube, you are asked to inhale as deeply as possible and exhale as hard as possible.
The procedure is repeated at least three times to obtain a constant and average value.
You will most likely not need recovery time after completing the FVC test. If you have severe lung disease and are dependent on supplemental oxygen and / or assistants to help you get around, you will need the same post-test care and support that you normally need.
But if you feel dizzy or short of breath, be sure to tell your healthcare team. When you recover, you may be asked to sit for a few minutes.
Also, if you have persistent or severe symptoms, you may need to monitor your oxygen levels. If it is low, you will be given supplemental oxygen.
interpretation of results
Your total FVC can be compared to the standard FVC for your age, gender, height, and weight. Your FVC can also be compared to your previous FVC values, if applicable, to determine if your lung condition is progressing or your lung function improves with treatment.
The forced vital capacity of the lungs will be communicated in two ways:
- Absolute value in liters (l).
- On a line graph to show the dynamics of your exhalation.
The normal range of FVC for an adult is 3.0 to 5.0 liters.
For children, the expected FVC can be predicted using look-up tables that include the child's height, body weight, and other factors. For example, the standard FVC for a medium-sized preschool boy is 1.16 liters and 1.04 liters for a medium-sized preschool girl.
The FVC can also be expressed as a percentage of the predicted FVC.
The forced vital capacity of the lungs can be temporarily or permanently reduced. A decrease in FVC is a sign of several conditions, including:
- Chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis , emphysema, and bronchiectasis.
- Restrictive airway diseases such as idiopathic pulmonary fibrosis.
- Structural restrictive airway diseases, such as those caused by scoliosis and scars on the chest.
- Diseases such as sarcoidosis.
- Inflammatory lung diseases such as asbestosis and silicosis.
- Lung cancer
FEV1 / FVC ratio
Your FVC value can be used to calculate your FEV1 / FVC ratio . The FEV1 to FVC ratio compares the amount of air that can be displaced in one second with the amount that can be released as a whole. The normal FEV1 / FVC ratio is 70 to 80% or more in adults and 85% or more in children.
The FEV1 / FVC ratio can help determine whether the lung condition is obstructive (eg, in COPD) or restrictive (eg, in pulmonary fibrosis ). Any change in the FEV1 / FVC ratio can provide valuable information on whether pulmonary obstruction and / or pulmonary restriction occurs.
Although restrictive diseases restrict air intake, they do not affect expiratory force. In contrast, obstructive disease can make exhalation difficult, but does not necessarily alter the volume of the airways.
If both the FEV1 / FVC and FVC ratios are low, the person has a mixed defect with limitation and obstruction.
You may need additional testing after your FVC has been done or after your FVC / FEV1 ratio has been calculated.
For example, respiratory symptoms with a normal FEV1 / FVC ratio are restrictive and you may need to undergo complete lung function tests and imaging tests, such as chest / lung computed tomography (CT).
If the FEV1 / FVC ratio is low, indicating obstructive lung disease, your healthcare provider may repeat the bronchodilator test to see if the obstruction is reversible. An obstructive condition like asthma tends to be reversible, while a condition like COPD is not.
If you are diagnosed with a lung disease that affects FVC, you may need to repeat this test periodically so your health care team can monitor your condition.
Get the word of drug information
While FVC is a valuable metric for evaluating lung disease, it is important to remember that it is just a number. Your healthcare provider will want to look at your health, overall health, and other results to see how your FVC measurements fit into your overall health picture.