FEV1, or forced expiratory volume, is a measurement taken from a pulmonary function test. It calculates the amount of air that a person can force out of their lungs in 1 second.
Working out a person's FEV1 value can help in the diagnosis of a chronic lung disease, such as chronic obstructive pulmonary disease (COPD). FEV1 and other measurements also allow doctors to understand how severe the disease is, and track its progression over time.
This article explains the role of FEV1 values in the staging, diagnosis, and management of COPD.
It can involve inflammation and mucus in the airways or damage to the lungs, both of which lead to breathing difficulties.
People already diagnosed with COPD, or those suspected of having COPD or a related condition should undergo a pulmonary function test to determine their FEV1 value.
A pulmonary function test is also called a spirometry test. It involves breathing forcefully into a mouthpiece.
FEV1 values that are lower than average suggest the presence of COPD or another condition that is causing breathing difficulties.
Normal FEV1 values vary between individuals, and can depend on the following factors:
It is possible to get an estimated normal FEV1 value from the spirometry reference value calculator provided by the Centers for Disease Control and Prevention (CDC). This will give a predicted reading based on average values of healthy people of the same age, gender, height, and race.
People who already know their FEV1 value can enter it into the CDC calculator to see their results as a percentage of the predicted average value for their status.
In COPD, lower FEV1 results typically suggest more severe disease.
The FEV1 reading is just one measurement taken from a pulmonary function test. The FVC, or forced vital capacity, is another important reading.
The FVC shows the amount of air that a person can breathe out, quickly and forcefully, after a deep breath. The FEV1 measurement is recorded during the first second of the FVC test.
As with FEV1 readings, the FVC results are compared with average values from healthy individuals that have the same age, height, and weight as the person being tested. Lower FVC readings can indicate more advanced stages of COPD.
The ratio of FVC and FEV1 can help doctors diagnose the specific type of lung disease a person has. To calculate this ratio, a doctor divides the FVC reading by the FEV1 result.
According to the Lung Institute, when an FEV1 value is less than 80 percent of an FVC, it indicates that an obstructive lung disease, such as COPD, is present.
People who already have a COPD diagnosis can determine the stage of their disease using their FEV1 result. To do this, a person will need to calculate the FEV1 reading as a percentage of the predicted value for healthy individuals of the same age, gender, height, and race.
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) define COPD based on the following FEV1 percentages:
|GOLD stage of COPD||Percentage of predicted FEV1 value|
|Mild||80 percent or above|
|Moderate||50 to 79 percent|
|Severe||30 to 49 percent|
|Very severe||29 percent or less|
However, GOLD note that there is a weak association between FEV1, a person's symptoms, and their health status. As a result, a doctor's assessment of symptoms is also important in the COPD staging process.
FEV1 is used in association with other tests to help diagnose COPD.
A COPD diagnosis may involve:
- FEV1 reading
- FVC reading
- FEV1/FVC ratio
- assessment of symptoms
- medical and family histories
- imaging tests, such as X-rays or computed tomography (CT) scans
- an arterial blood gas test, to test blood oxygen levels
Many doctors also use a COPD assessment test (CAT) to find out how COPD affects a person's life. Doctors will use the result of the CAT alongside other test results to determine the stage and severity of the COPD.
COPD is a progressive disease, meaning that it gets worse over time. Follow-up pulmonary function tests are carried out on people with COPD to track how the disease progresses, which varies from person to person.
The results of these tests will help the individual and doctor understand how the COPD is progressing over time.
Doctors also use these results when deciding on any treatment plan changes and when making recommendations about a person's lifestyle.
Many experts recommend rechecking FEV1 scores whenever a person with COPD experiences significant changes in their symptoms rather than having a routine schedule for pulmonary function tests.
Those who smoke may require more testing, as their symptoms are more likely to progress when compared with people who do not smoke.
What steps can someone with COPD take?
People with COPD should regularly attend their medical appointments, and complete recommended pulmonary function tests. Also, knowing their FEV1 and FVC readings will help them understand the severity of their condition.
These results help guide the treatment plan, which the person should follow carefully.
There are other steps a person with COPD can take to relieve symptoms and slow disease progression. These include:
- quitting smoking, the most common cause of COPD
- eating a healthful diet
- doing regular physical activity
- participating in a pulmonary rehabilitation program
- avoiding exposure to irritants, such as air pollution, chemical vapors, and dust
- using oxygen therapy as prescribed
It is also vital to inform a doctor if a person notices any changes in symptoms. Symptoms of COPD flare-ups include worsening:
- breathing difficulties
- chest tightness
- coughing and mucus production
- difficulty exercising or engaging in everyday activities
- shortness of breath
FEV1 is a very useful measurement that is taken during a pulmonary function test. The FEV1 value can be used alongside other tests to diagnose COPD and other lung diseases.
FEV1 also helps in the staging and management of the disease and allows doctors to monitor COPD progression over time. As a person's lung capacity changes, so do their FEV1 measurements.
Most people with COPD will need to undergo follow-up pulmonary function tests to check their FEV1, although smokers or people who experience changes in COPD symptoms may require more frequent testing.