Spirometry: procedure, "normal" values ​​and test results (2023)

Spirometry is a standard test that doctors use to measure how well your lungs are working. The test measures the flow of air going in and out of the lungs.

To perform a spirometry test, you sit and breathe into a small machine called a spirometer. This medical device records the amount of air inhaled and exhaled, as well as the respiratory rate.

Doctors use spirometry tests to do this.to diagnosethese conditions:

  • COPD
  • Asma
  • restrictive lung disease, such as interstitial pulmonary fibrosis
  • other diseases that affect lung function

They also allow your doctor to monitor chronic lung conditions to see if your current treatment is improving your breathing.

Spirometry is often performed as part of a group of tests known aslung function tests.

There are a number of things you can do to ensure that you can breathe comfortably and get an accurate result during your spirometry test.

Consider these tips:

  • Wear loose clothing.
  • If you smoke, refrain from smoking for at least 1 hour before the test.
  • If you drink alcohol, please refrain from drinking for at least 4 hours before the test.
  • Avoid eating or drinking for at least 2 hours before the test.
  • Avoid strenuous physical exertion or exercise for at least 30 minutes before the test.
  • Consult with a doctor about avoiding medications such as inhalers before the test, as they may affect the accuracy of the results.

A spirometry test usually takes around 15 minutes and is usually done in your doctor's office. In some cases where more in-depth testing is needed, it may be done in a respiratory laboratory.

(Video) Spirometry Results Explained

This is what happens during a spirometry procedure:

  1. You are sitting in a chair in an exam room at your doctor's office. The doctor or nurse will place a nose clip to keep both nostrils closed. They also place a cup-shaped breathing mask around the mouth.
  2. Your doctor or nurse will then instruct you to take a deep breath, hold your breath for a few seconds, and exhale as hard as you can into the respirator.
  3. You will repeat this test at least three times to ensure that your results are consistent, especially if there are large differences between your test results. It takes the highest value of three close test readings and uses it as the final result. Your entire engagement should last approximately 30 to 90 minutes.

If you have signs of a breathing disorder, your doctor may give you an inhaled medication known as a bronchodilator to open up your lungs after the first round of tests.

You will then be asked to wait 15 minutes before taking another series of measurements. Your doctor will then compare the results of the two measurements to see if the bronchodilator helped increase airflow.

When monitoring for respiratory disorders, a spirometry test is usually performed.once every 1 or 2 yearsto monitor respiratory changes in people with well-controlled COPD or asthma.

People with more severe breathing difficulties or respiratory complications that are not well controlled are advised to have more frequent spirometry tests.

Usually, there are few complications during or after a spirometry test. However, please note the following.

As a result, you may feel slightly dizzy or out of breath immediately after taking the test.american thoracic society. If this happens, stop immediately and tell your doctor. In very rare cases, the test can cause serious breathing problems.

When you perform this test, the pressure in your head, chest, abdomen, and eyes increases as you exhale. that's how it isinsecureif you have heart problems or high blood pressure, or if you have had surgery on your chest, abdomen, head or eyes.

Risks after a spirometry test

(Video) How to do a spirometry test and interpret the results

There are few risks associated with the spirometry test itself, but there is a small risk of indirect infection.

This can be done in different ways:

  • Although data is generally not available on spirometer disinfection, there may be concerns that people are at risk of infection with a variety of fungal microorganisms if the spirometer tube is not adequately disinfected after each test. These include respiratory illnesses such as the flu, measles, chickenpox, pneumonia, and tuberculosis. according to aResearch Review 2015, researchers have found bacterial growth in the spirometer tube in at least one study.
  • Other equipment, such as breathing valves and mouthpieces, can also transmit infections. It must be disinfected and changed between patients. Also, you need to be careful with the infrastructure of the lab: the chair you sit on, nearby tables and surfaces, and anything else you might come into contact with. Use hand sanitizer liberally and wash your hands after testing. This can also help protect you from the coronavirus that causes COVID-19 and other viruses.
  • Because aerosolized particles are inhaled during spirometry, there is a risk of spreading airborne viral illnesses. This risk applies to both medical personnel and patients who can breathe air if a previous patient is present. While a variety of diseases can be spread through the air, the biggest concern right now is the coronavirus that causes COVID-19. Talk to your doctor before the test if you think this might be the case.COVID-1 symptoms.
  • People with cystic fibrosis need more frequent lung function tests. However, they are also at increased risk of upper respiratory tract infection when they come in contact with the test kit and the personnel administering the test.

This risk may be higher in other countries that have different standards and protocols to prevent the spread of infection.

An American Thoracic Society and a European Respiratory Societyhave official technical standardsto perform spirometry. This includes disinfection guidelines and the recommendation of disposable face masks with filters to prevent contagion.

The “normal” results of a spirometry test vary from person to person. They are based on your:

  • to alter
  • Height
  • carrera
  • Sex

Your doctor will calculate the expected "normal" value for you before performing the test. After running the test, look at the test result and compare that value to the expected result. Your result is considered "normal" if your score is80 percentor more than the predicted value.

Spirometry measures two main factors: forced expiratory vital capacity (FVC) and forced expiratory volume in one second (FEV1). Your doctor also considers this a combined number known as the FEV1/FVC ratio.

When you have a blocked airway, the amount of air you can quickly push out of your lungs is reduced. This leads to a lower FEV1 and FEV1/FVC ratio.

FVC measurement

One of the main measures of spirometry is FVC, which is the greatest total amount of air you can forcefully exhale after taking your deepest breath in. If your FVC is lower than expected, something is restricting your breathing.

"normal" or "abnormal"Resultsthey are evaluated differently by adults and children.

For children from 5 to 18 years old:

(Video) Understanding Spirometry - Normal, Obstructive vs Restrictive

Percentage of predicted FVC valueResult
80% or morenormal
less than 80%it is not normal

For adults:

is greater than or equal to the lower limit of normalnormal
is less than the lower limit of normalit is not normal

An "abnormal" FVC can be caused by restrictive or obstructive lung disease, and other types of spirometry measurements are needed to determine what type of lung disease is present.

Obstructive or restrictive lung disease may be present alone, but a mixture of both forms at the same time is also possible.

FEV1 measurement

The second important measure of spirometry is FEV1. This is the amount of air you can blow out of your lungs in 1 second.

It can help your doctor assess the severity of your breathing problems. A lower than expected FEV1 value indicates that you may have significant respiratory failure.

Your doctor will use your FEV1 measurement to assess the severity of your breathing difficulties. The table below shows what is considered to be your FEV1 spirometry test results according to the guidelines of theamerican thoracic society:

Percentage of predicted FEV1 valueResult
80% or morenormal
70%–79%slightly abnormal
60%–69%moderately abnormal
50%–59%moderately to severely abnormal
35%–49%completely abnormal
less than 35%very strongly abnormal

FEV1/FVC ratio

Doctors usually look at FVC and FEV1 separately and then calculate your FEV1/FVC ratio. The FEV1/FVC ratio is a number that represents the percentage of your lung capacity that you can exhale in 1 second.

In the absence of a restrictive lung disease causing a normal or elevated FEV1/FVC ratio, the higher the resulting percentage of your FEV1/FVC ratio, the healthier your lungs will be.

Alow indexindicates that something is blocking your airway. The following are considered a low score:

to alterLow FEV1/FVC ratio
5 to 18 yearsless than 85%
Adultless than 70%

Spirometry creates a graph that shows your airflow over time. If your lungs are healthy, your FVC and FEV1 values ​​will be plotted on a graph that might look like thisSo:

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If your lungs have become blocked in some way, your diagram might look like this:

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(Video) Spirometry: Procedure and Results

If your doctor determines that your results fall into the "abnormal" category, they will likely run other tests to determine if your restricted breathing is caused by a respiratory disorder. This may includechest x-rays,X-rays of the breastsand blood tests.

Primary lung diseases that lead to unexpected spirometry results include obstructive diseases, such as asthma and COPD, and restrictive diseases, such as interstitial pulmonary fibrosis.

Your doctor may also look for medical conditions, often associated with respiratory disorders, that could make your symptoms worse. These includeAsia,allergic rhinitis, misinus infection.

Read more: How spirometry results track the progress of COPD.

Read this article in Spanish.

(Video) Pulmonary Function Test (PFT) Explained Clearly - Procedure, Spirometry, FEV1


What are normal values for spirometry test results? ›

The Measured column represents the total volume exhaled during the first second, in liters. Normal values in healthy males aged 20-60 range from 4.5 to 3.5 liters, and normal values for females aged 20-60 range from 3.25 to 2.5 liters.

What is FEV1 FVC normal value? ›

Normal findings of spirometry are an FEV1/FVC ratio of greater than 0.70 and both FEV1 and FVC above 80% of the predicted value. If lung volumes are performed, TLC above 80% of the predictive value is normal. Diffusion capacity above 75% of the predicted value is also considered normal.

What a spirometry test score can tell you about your COPD? ›

Path to improved health

Spirometry is a type of pulmonary function test. It measures how well your lungs are working. Your doctor uses the test results to help determine whether you have COPD or other possible lung disease. If you have COPD, the results also show how severe your COPD is.

What do spirometry test results mean? ›

Spirometry test results help your healthcare provider determine: If your symptoms are the result of asthma or another condition. If there's a blockage or narrowing in your airways. If treatment is working. If your lungs are lower in volume than normal, which may require more testing.

What is a normal lung function test result? ›

What will the results look like? Lung volume is measured in litres. Your predicted total lung capacity (TLC) is based on your age, height, sex and ethnicity, so results will differ from person to person. Normal results typically range between 80% and 120% of the prediction.

What is a good lung function test result? ›

Normal results typically range between 80% and 120% of the prediction. If your lung volume results fall outside of this normal range, this may suggest you have an obstructive or restrictive lung condition.

What FVC value indicates a lung problem? ›

The FEV1 is used with the FVC to differentiate between obstructive lung disease (FEV1/FVC < 70%) and restrictive lung disease (reduced FEV1 and FVC but normal FEV1/FVC relationship). An FEV1 of less than 1 L indicates significant lung disease.

What does FEV1 FVC 70% mean? ›

This is a measure of how quickly the lungs can be emptied. • FEV1/FVC: FEV1 expressed as a percentage of the FVC, gives a clinically. useful index of airflow limitation. The ratio FEV1/FVC is between 70% and 80% in normal adults; a value less than 70% indicates airflow limitation and the possibility of COPD.

How do you interpret FEV1 and FVC? ›

A low FEV1/FVC ratio (the forced expiratory volume in 1 second divided by the forced vital capacity) indicates an obstructive pattern, whereas a normal value indicates either a restrictive or a normal pattern.


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