Forced expiratory volume (FEV1) calculates the amount of air that a person can force out of their lungs in 1 second. FEV1 values that are lower than average suggest the presence of COPD.

Working out a person’s FEV1 value can help diagnose chronic lung diseases, such as chronic obstructive pulmonary disease (COPD). FEV1 and other measurements also allow doctors to understand how severe the condition is and to track its progression over time.

This article explains the role of FEV1 values in the staging, diagnosis, and management of COPD.

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COPD is a term that refers to certain medical conditions that affect breathing, such as chronic bronchitis and emphysema.

It can involve inflammation and mucus in the airways or damage to the lungs, both of which lead to breathing difficulties.

People with a COPD diagnosis or those who may have COPD or a related condition should undergo a pulmonary function test to determine their FEV1 value.

A pulmonary function test, also known as a spirometry test, 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:

  • age
  • gender
  • height
  • race

It is possible to get an estimated normal FEV1 value from the spirometry reference value calculator that the Centers for Disease Control and Prevention (CDC) provide. This will give a predicted reading based on average values from healthy people of the same age, gender, height, and race.

Individuals 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 a more severe condition.

The FEV1 reading is just one measurement taken from a pulmonary function test. Forced vital capacity (FVC) is another important reading.

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 of the same age, height, and weight as the person undergoing testing. 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.

When the value of FEV1 is less than 70% of an FVC in adults or below 85% in those aged 5–18 years, an obstruction may be present. It may be a sign of COPD.

If a person already has a COPD diagnosis, their FEV1 result can help them and a doctor determine the stage of the condition.

To do this, the 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) defines COPD based on the following FEV1 percentages:

COPD stagePredicted FEV1 value
mild80% or above
very severe29% or less

However, the GOLD notes 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:

  • a FEV1 reading
  • an FVC reading
  • a FEV1/FVC ratio
  • an assessment of symptoms
  • medical and family histories
  • imaging tests, such as X-rays or 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 COPD.

COPD is a progressive condition, meaning that it worsens over time. Follow-up pulmonary function tests are carried out in people with COPD to track how the condition progresses, which varies from person to person.

The results of these tests will help the individual and the doctor understand how 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.

Individuals 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 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 an individual with COPD can take to relieve symptoms and slow disease progression. These include:

  • quitting smoking
  • eating a balanced diet
  • engaging in regular physical activity
  • participating in a pulmonary rehabilitation program
  • avoiding exposure to common 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
  • wheezing

FEV1 is a 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 conditions.

FEV1 also helps in the staging and management of a person’s condition and allows doctors to monitor COPD progression over time. As an individual’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. People who smoke may require more frequent testing.