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Table of Contents
Purpose of Test
Risks and Contraindications
Before the Test
During the Test
Interpreting Results
Spirometry, a type ofpulmonary function test (PFT), is a non-invasive procedure that can provide information about how well your lungs are working. It measures how much and how quickly the air you exhale (breathe out) moves as you breathe into a tube. Spirometry is used to diagnose respiratory conditions such asasthma, and to monitor lung diseases to evaluate how well treatment is working.
Sometimes spirometry is done in conjunction with other PFTs.
It can help determine whether a lung condition is obstructive (in which exhalation is impaired) or restrictive (in which inhalation is impaired).
Spirometry is rarely used alone to diagnose a lung condition. It is typically combined with other findings, such as a physical exam, medical history review, and imaging tests, to reach a diagnosis.
As part of a panel of PFTs, spirometry may be used to help diagnose:
Spirometry is also useful for evaluating whether lung diseases are getting better, worse, or staying the same. This can help determine if a treatment is working or needs to be modified.
Spirometry may also be used before lung cancer surgery to predict how the lungs will function after a portion or lobe of a lung is removed.
How COPD Is Diagnosed
Spirometry is a very safe procedure, but you may become short of breath or feel a little lightheaded while taking the rapid, deep breaths that are required. You may also experience coughing. These symptoms are normal and rarely a cause for concern.
People with asthma are at a small risk of an asthma attack during spirometry. In such instances, the exertion can cause temporary, sudden, and severe breathing problems.
Contraindications
People should not undergo a spirometry test if they:
There are certain conditions under which a person may not be able to breathe fully and deeply, potentially altering the accuracy of the test.
The conditions include:
While not necessarily contraindications, an evaluation from a healthcare provider may be required before the test can proceed.
What Healthcare Provider Should I See About Asthma?
Being aware of what’s involved in a spirometry test can help you prepare and achieve the most accurate results.
Timing
A spirometry test typically takes around 45 minutes. It can take longer depending on waiting times. Ask your healthcare provider if the test may take longer so that you' can plan ahead.
Location
Spirometry is usually done in a pulmonologist’s or allergist’s office or at a hospital as an outpatient procedure.
At-home spirometry testing machines are available for healthcare provider-supervised monitoring of a lung condition.
What to Wear
Because you will need to take very deep breaths, you should dress in loose-fitting clothing that won’t restrict your breathing. Don’t wear a belt or clothing that fits tightly around your chest or waist.
Food, Drink, and Medications
Little preparation is required before having a spirometry test. However, your healthcare provider may advise you to:
Cost and Health Insurance
If you have health insurance, a spirometry test that’s considered medically necessary will be partially or fully covered, depending on the terms of your policy. You also may be responsible for a co-pay or coinsurance. Prior authorization may be needed.
If you don’t have insurance, your out-of-pocket cost for a spirometry test can range from $40 to $800, depending on where you are having the test and the tests that are done.
What to Bring
Bring your insurance card, ID, and form of payment to your spirometry test appointment.
Other Considerations
Here are a few other things you should do before having a spirometry test to ensure the most accurate results:
Pre-Test
After you arrive for your appointment, you will check in. This may involve filling out consent forms, having your insurance card photocopied for your files, and taking care of your co-pay if you have one.
When you are called for your test, you will be asked to empty your bladder. You will then be escorted to the room where PFTs are performed. The technician or respiratory therapist will typically record your height since this will influence how the tests are interpreted.
You’ll be instructed to loosen your belt, if wearing one, and to remove any clothing or jewelry that restricts breathing. If you wear dentures, you will leave them in for the test.
Throughout the Test
You will be seated in a chair for the spirometry test and asked to sit and breathe normally to settle in. When ready, the technician will place a clip on your nose so that you only breathe through your mouth.
Most likely you’ll be given a tube-like mouthpiece to breathe into. This will be connected to a spirometer, a machine roughly the size of a home printer that measures the force and volume of your breaths. Less commonly, there are portable devices about the size of a camera with a mouthpiece and digital read-out.
The technician will give you specific instructions on how to place your lips around the mouthpiece to create a tight seal. You will then be asked to take as big and deep a breath as possible and to blow into the tube as forcefully as you can.
The spirometer will create a graph that records the speed and amount of air as you breathe. To be considered accurate, the tests must be reproducible (meaning the same results are achieved repeatedly). So you’ll be asked to repeat the test a minimum of three times.
Among the things that can potentially alter results:
If there are signs of respiratory obstruction, a short-acting bronchodilator like albuterol may be used on a second round of testing to open the airways and see if the results improve.
If you feel dizzy or lightheaded, or can’t stop coughing, let the technician know. In most cases, all you will need is a short break to recover.
After a spirometry test, you can return to your normal activities and use any medications you may have stopped.
What Is a Lung Diffusion Test?
Since the results of your test are immediately available, your healthcare provider will likely be able to review them with you at your appointment.
Spirometry provides two important measurements of lung function:
All three FEV1 measurements and all three FVC measurements must be within 200 milliliters (ml) of each other. If they aren’t, the test will not meet the reproducibility criteria, and you may need to start all over again.
When the healthcare provider is satisfied that the test results are valid, the information will be used to determine if lung function is normal or abnormal.
Abnormal results indicate one of three possible breathing patterns:
Obstructive Disease
Obstructive lung disease is one in which damage to the lungs and narrowing of the airways make it harder to exhale. An obstructive pattern is seen in lung conditions such as COPD and asthma.
When the airways are obstructed, the amount of air you can exhale in one second (FEV1) is less than would be expected for someone your age and height.
The definition of airway obstruction is a lowFEV1/FVC ratio.The normal level is age-based:
Restrictive Disease
A restrictive lung problem means that the lungs contain too little air and do a poor job of transferring oxygen into the blood. Restrictive diseases are most often the result of a condition causing stiffness in the lungs.
There is extra-thoracic restriction and intra-thoracic restriction. The most common reason for restrictive disease on spirometry is extra-thoracic, and includes anything that doesn’t allow the lungs to fully expand. This includes obesity,scoliosis(abnormal curvature of the spine), diaphragmatic paralysis, and pleural effusion.
Intra-thoracic restriction includes diseases of the lung parenchyma, including fibrosis. Sarcoidosis (an inflammatory disease that causes abnormal growths in tissue) causes mixed airway obstruction and restriction.
Treating Obstructive and Restrictive Lung Diseases
Obstructive/Restrictive Disease
A combination of both obstructive and restrictive breathing patterns may be seen when a person has more than one lung disease, such as cystic fibrosis with asthma or sarcoidosis with COPD.
If you have COPD, the results of a spirometry test after the use of a bronchodilator can establish how severe your disease is and whether or not it is progressing.
Different Types of Asthma: Which One Do You Have?
If your spirometry test results don’t help determine if an obstructive and/or restrictive lung disease is involved, your healthcare provider may order other PFTs, such asplethysmography, to measure your total lung capacity.
If a definitive diagnosis is reached, the next step would be to address treatment options and, in some cases, undergo additional tests to characterize and stage the disease.
How Lung Cancer Is Diagnosed
Home Spirometry
A home spirometry unit—basically a scaled-down version of the type used in clinical settings—can be useful under certain circumstances with the oversight of a healthcare provider.
A home device allows you to regularly monitor trends in your breathing patterns over a period of time to report back to your practitioner. This information may help your medical professional to fine-tune your treatment more precisely than is possible with a single office visit.
It’s important not to use a home spirometer as a substitute for regular medical visits or to make your own treatment changes based on the readings.
Note that there is a simpler type of spirometer called anincentive spirometerthat does not provide measurements of lung function. It’s a device designed to help keep the lungs clear after surgery.
Home Pulse Oximeters for People With Asthma
A Word From Verywell
If you have undergone a spirometry test, you can ask your healthcare provider to explain the findings to you, what the numbers mean, and if there have been any changes in value since your last visit. The results of your test, along with your symptoms, can help In the diagnosis of your breathing problem. And changes to your test results over time may help guide your treatment.
9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Braun L.Race, ethnicity and lung function: A brief history.Can J Respir Ther.
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Odeyemi YE, Lewis O, Ngwa J, Dodd K, Gillum RF, Mehari A.Does Low FEV1 in addition to fixed ratio and/or lower limit of normal of FEV1/FVC improve prediction of mortality in COPD? The NHANES-III-linked-mortality cohort.J Natl Med Assoc. 2019;111(1):94-100. doi:10.1016/j.jnma.2018.06.006
Chhabra SK.Clinical application of spirometry in asthma: Why, when and how often?.Lung India. 2015;32(6):635-7. doi:10.4103/0970-2113.168139
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