FEV1/FVC Ratio in Spirometry

The FEV1/FVC ratio is a measurement of the amount of air you can forcefully exhale from your lungs. FEV1, or forced expiratory volume in one second, is the volume of breath exhaled with effort in that timeframe. FVC, forced vital capacity, is the full amount of air that can be exhaled with effort in a complete breath.

Also known as Tiffeneau-Pinelli index, FEV1/FVC ratio is often used in in diagnosing and treating obstructive lung diseases such as chronic obstructive pulmonary disease (COPD).

Elderly male patient using spirometer device

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The Purpose of a Lung Function Test

Once your doctor has determined that you have a lung condition, they will often assess your FEV1/FVC ratio to identify the primary type of condition you may have and, specifically, whether it is restrictive or obstructive in nature.

Restrictive lung diseases (such as pulmonary fibrosis) affect one's ability to inhale, while obstructive conditions (such as asthma and COPD) affect one's ability to exhale.

The ratio itself is a more indicative diagnostic tool than either measurement alone.

It may also be used to monitor your disease in the long run, too, 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 doctor's office and takes about 45 minutes.

Risks and Contraindications

Spirometry is a very safe, noninvasive test that involves breathing into a tube attached to a meter that measures airflow and force. However, you may feel lightheaded or short of breath when blowing forcefully, or you may start to cough.

Those who have asthma are at a small risk of having an asthma attack during the test, and there is also a slight risk that breathing with strong exertion could cause severe yet temporary breathing problems. However, since the test is performed under medical supervision, your practitioner will be able to 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 FEV1/FVC Results

Doctors may use various tests to determine the severity of your condition. Spirometry is one test that helps measure lung function by analyzing 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: the percentage of the FVC expired in one second.

Then your test result is compared to the predicted value, which represents a normal result based on your age, weight, and sex.

Decreased FVC With Proportional FEV1/FVC Ratio

If your FVC is decreased but the ratio of FEV1/FVC is normal, this indicates a restrictive pattern. A normal ratio is 70% to 80% in adults and 85% in children.

Restrictive lung concerns may be those in which the lung tissue itself is damaged, or when structurally someone is unable to breathe as deeply as normal. 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 cause a restrictive pattern by limiting 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
  • COPD, including chronic bronchitis, emphysema, and bronchiectasis
  • Bronchiolitis

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:

Abnormal FEV1 and FVC Results
FEV1/FVC Ratio Severity of Condition
> 70% Mild
60 to 69% Moderate
50 to 59% Moderately Severe
35 to 49% Severe
< 34% Very Severe

Follow-Up

If a restrictive pattern is observed, doctors 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, a medication that helps to reduce constriction of the airways.

If you are being treated for obstructive lung disease, your doctor 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.

Frequently Asked Questions

What FEV1 and FVC percentages are normal in spirometry test results?

A normal ratio is considered to be 70% to 80% in adults, and 85% in children. Keep in mind that your age, weight, and sex are taken into account when establishing what is normal for you.

Will exercise impact FEV1 and FVC levels?

Yes, exercise should have a positive effect. Studies have shown that high-intensity aerobic exercise done regularly over a period of weeks or months can improve lung function as measured by FEV1 and FVC levels. However, if you have a lung condition, always check with your doctor before beginning an exercise program.

Will smoking affect my FEV1 and FVC levels?

Yes. Research has shown that FEV1 and FVC levels are negatively affected by smoking, and worse in those who have smoked for a longer period of time and/or have smoked more cigarettes overall.

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 doctor will also look at your general health, lifestyle, and other factors to thoroughly assess your condition and come up with a treatment plan that's customized for you.

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