FEV1/FVC Ratio in Spirometry

The FEV1/FVC is a ratio that reflects the amount of air you can forcefully exhale from your lungs. It's measured by spirometry, a test used to evaluate lung function.

The FEV1/FVC ratio is often used in diagnosing and monitoring the treatment of lung diseases such as chronic obstructive pulmonary disease (COPD).

It's made up of two measurements:

• FEV1: Forced expiratory volume in one second, or the volume of breath exhaled with effort in one second
• FVC: Forced vital capacity, or the full amount of air that can be exhaled with effort in a complete breath

This article discusses the purpose of measuring the FEV1/FVC ratio. It covers how the results are interpreted and what kinds of follow-up tests may be needed.

Purpose of FEV1/FVC Test

Once your healthcare provider has determined that you have a lung condition, they will assess your FEV1/FVC ratio. This helps identify the type of condition you have and whether it is restrictive or obstructive.

• Restrictive lung diseases (such as pulmonary fibrosis) affect your ability to inhale
• Obstructive conditions (such as asthma and COPD) affect your ability to exhale

This test is often used to monitor lung disease, especially if you have an obstructive condition such as asthma. Measuring your FEV1/FVC ratio at regular intervals can help assess how well treatment is working or how your condition is progressing.

FEV1/FVC is just one of several measurements taken when using a spirometer. The test can be done in your healthcare provider's office and takes about 45 minutes.

Risks and Contraindications

Spirometry is a safe, non-invasive test. It involves breathing into a tube attached to a meter that measures airflow and force.

Some people may feel lightheaded or short of breath when blowing forcefully or may start to cough.

If you have asthma, there is a small risk of having an asthma attack during the test. There is also a slight risk that breathing with strong exertion could cause temporary, yet severe breathing problems.

However, since the test is performed under medical supervision, your practitioner can help manage any situations that may arise.

Contraindications

If you have any of the following conditions, a spirometry test is not recommended:

• Chest pain, recent stroke, or heart attack
• Collapsed lung (pneumothorax)
• Recent eye surgery, or chest or abdominal surgery, as deep breathing could affect the pressure in those areas
• Aneurysm (bulging blood vessel) in the brain, chest, or abdomen
• Current or recent respiratory infection or tuberculosis

Interpreting Results

Healthcare providers may use various tests to determine the severity of your condition. Spirometry is one test that helps assess lung function by measuring the force of your breath.

In measuring FEV1/FVC via spirometry, the amount of air you exhale in one second is recorded, as well as the total amount of air you are able to exhale. The ratio of these two values is expressed as a percentage. This is the percentage of the FVC exhaled in one second.

Your test result is compared to the predicted value, which represents a normal result based on your age, height, and sex. A normal ratio is 70% to 80% in adults and 85% in children.

Decreased FVC With Normal FEV1/FVC Ratio

If your FVC is decreased but the ratio of FEV1/FVC is normal, this indicates a restrictive pattern.

Restrictive lung problems occur when a person can't breathe in as deeply as normal. They are associated with lung tissue damage.

Some examples include:

• Pulmonary fibrosis, such as idiopathic pulmonary fibrosis, a scarring of the lungs of uncertain cause
• Deformities of the chest such as scoliosis or chest wall scarring
• Results of lung cancer surgery, such as a lobectomy or pneumonectomy
• Infections and inflammatory diseases such as pneumonia, tuberculosis, sarcoidosis, silicosis, and asbestosis
• Neurological disorders such as amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease)
• Pleural effusion, in which fluid builds up in the area between the lungs and the chest wall
• Ascites, fluid buildup in the abdomen due to liver disease or cancer can limit the ability to take a deep breath

Decreased FEV1/FVC Ratio

If your FEV1/FVC ratio is decreased, this is consistent with an obstructive pattern.

Usually, this diagnosis is reached if the FEV1/FVC is less than or equal to 70% in adults and less than 85% in children.

Damage and/or constriction of the airways is indicative of conditions such as:

• Asthma, a long-term condition where the airways become constricted and inflamed
• COPD, a progressive lung disease, which includes chronic bronchitis and emphysema

Assessing the Severity

If the FEV1/FVC ratio is found to be abnormal, the next step is grading the abnormality to determine the severity of the condition. The American Thoracic Society has set specific guidelines for this purpose:

Follow-Up

Your follow-up is determined by the results of the test, as well as your symptoms, medical history, and other diagnostic tests.

• If a restrictive pattern is observed, healthcare providers will usually recommend more extensive pulmonary function tests to further characterize your lung disease.
• If an obstructive pattern is found, the next step is usually to recommend treatment with a bronchodilator. This is a medication that helps to reduce constriction of the airways.

If you are being treated for obstructive lung disease, your healthcare provider will most likely monitor your progress by retesting your FEV1/FVC ratio.

If the ratio improves with a bronchodilator, that means that the obstruction is at least partially reversible. This is usually seen with conditions such as asthma.

If the ratio does not improve with a bronchodilator, it may be irreversible, such as is often seen in COPD.

Summary

The FEV1/FVC ratio indicates how much air you can forcefully exhale. It's measured by spirometry, a test used to diagnose or monitor lung conditions.

The FEV1 measures how much air you can exhale in one second. The FVC measures the total amount of air you can exhale forcefully in one breath.

Your healthcare provider can use the FEV1/FVC ratio to help determine if you have a restrictive or obstructive lung condition. If you have a restrictive condition, you may need more pulmonary function tests to help diagnose your condition.

If your lung condition is obstructive, your healthcare provider may recommend using a bronchodilator as a treatment to see if it improves your ratio.

A Word From Verywell

The FEV1/FVC ratio is just one of several tests that can help diagnose your specific lung condition. It's easy to get caught up in a "good" or "bad" result, but it's just one small piece of information used to evaluate your disease.

Your healthcare provider will also look at your general health, lifestyle, and other factors to thoroughly assess your condition. That way, they can help you come up with a treatment plan that's customized for you.