What to Expect From a Spirometry Test

Spirometry is a type of pulmonary function test (PFT), a noninvasive procedure that provides important information about how well the lungs are working. It reveals how much and how quickly air is moving through the lungs ss you breathe into a tube. Spirometry is used to diagnose respiratory conditions, such as asthma, and to monitor lung diseases to evaluate how well a treatment is working. Sometimes spirometry is done in conjunction with other PFTs, depending on the specific information a doctor (usually a pulmonologist) is looking for.

what to expect during a spirometry test
Illustration by Emily Roberts, Verywell

Purpose of Test

Spirometry measures key aspects of pulmonary (lung) function. The test can play an important role in diagnosing and managing many lung problems. It can help distinguish between diseases with similar symptoms and determine whether the condition is obstructive (in which exhalation is impaired) and/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.

Spirometry, as part of a panel of PFTs, may be used to help diagnose:

Spirometry is also useful for evaluating disease progression (namely, whether it is 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 well a patient will tolerate the operation and manage once a portion or lobe of a lung is removed.

Risks and Contraindications

Spirometry is a very safe procedure, but you may become short of breath or feel a little lightheaded while taking rapid, deep breaths. 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 sudden and severe breathing problems, albeit temporarily.

Contraindications

People should not under a spirometry test if they:

  • Have chest pain or have recently had a heart attack or stroke
  • Have a collapsed lung (pneumothorax)
  • Had recent eye surgery (deep breathing increases eye pressure)
  • Had recent abdominal or chest surgery
  • Have an aneurysm in the chest, abdomen, or brain
  • Have tuberculosis (TB)
  • Have a respiratory infection, such as a cold or the flu

There are certain conditions under which a person may not be able to breathe as fully and deeply, potentially undermining the accuracy of the test. While not contraindications per se, they may require an evaluation from a doctor before the test can proceed. The conditions include:

  • Pregnancy
  • Stomach bloating
  • Extreme fatigue
  • General muscle weakness

Before the Test

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 doctor if the test may take longer so that you're neither rushing nor late for other appointments.

Location

Spirometry is usually done in the office of a pulmonologist (lung doctor) or at a hospital as an outpatient procedure. An overnight hospital stay may be required if the test is part of a more extensive procedure, such as lung surgery. In most cases, spirometry is performed by a pulmonary function technician or a respiratory therapist.

At-home spirometry testing machines are available but are typically recommended for the doctor-supervised monitoring of a lung condition (see below).

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. Avoid belts or clothing that fits tightly around the chest or waist.

Food, Drink, and Medications

There is not a lot of preparation involved in a spirometry test, but there are few things your doctor will likely advise you to do:

  • Eat lightly: If your stomach is too full, it may be harder to take deep breaths and you may end up getting sick.
  • Do not drink alcohol before the test: You may not be able to breathe as well if you have alcohol in your system.
  • Check that your medications won't interfere with the test: Certain drugs can affect breathing, particularly inhaled bronchodilators. Avoid short-acting inhalers six to eight hours before testing unless you really them (and then report any usage to the technician once you arrive).

Cost and Health Insurance

For people with health insurance, a spirometry test that's considered medically necessary will be covered at 80% to 100%, depending on the terms of your policy and how much of your deductible you've met. You also may be responsible for a co-pay or coinsurance.

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 live and the type of facility you use (e.g., public clinic, hospital, or private practice).

The average cost of spirometry is around $42, but be aware that this does not include the office visit, which could add another $25 to $100 (or more) to the total cost. Depending on your insurance provider and medical condition, prior authorization may be needed.

What to Bring

Aside from your insurance card, ID, and form of payment (if needed), you shouldn't need to bring anything in particular to a spirometry test. Double-check with the office to be sure and to find which form of payment is accepted.

Other Considerations

Here are a few other things you should do before having a spirometry test to ensure the most accurate results:

  • Go to bed early enough to get plenty of rest.
  • Do not smoke for at least four to six hours before the test.
  • Avoid heavy exercise or vigorous activity at least 30 minutes prior to testing.

During the Test

Here is a step-by-step description of what you are most likely to experience during a spirometry test, keeping in mind that there may be differences in equipment and how certain practitioners operate. Speak with your doctor in advance to better gauge your expectations.

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 then will be escorted to the room will PFTs are performed. The technician or respiratory therapist will typically take your height and weight since they will influence how the tests are interpreted (as can age, gender, and even ethnicity).

You'll be instructed to loosen your belt and 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 do all of your breathing through your mouth.

In most cases, 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 and fast as you can. You will be asked to do this at least three times.

The spirometer will create a graph that records the velocity and volume of your breath.

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 are improved.

Since you will be blowing hard and fast, you may develop dizziness, lightheadedness, or cough. Let the technician know if you experience any discomfort. 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.

Interpreting Results

Since the results of your test are immediately available, your doctor will likely be able to review them with you at your appointment.

The first step is to make sure the test is valid. This is important because there are a number of things that can go wrong during the test that can potentially nullify the results. Among them:

  • The person didn't create an adequate seal around the mouthpiece or placed the tongue incorrectly.
  • The person didn't fully understand the instructions, including pre-test preparations.
  • There was coughing during inhalation or exhalation.
  • The person wasn't able to put enough force into the exhalations (often because some diseases cause worsening pain with forceful breaths).
  • The mouthpiece was warped or damaged.

To be considered accurate, the tests must be reproducible (meaning that the same results are achieved during each sitting). That is why you'll be asked to repeat the test a minimum of three times.

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 the doctor may need to repeat the test.

When the doctor is satisfied that the test results are valid, the information will be used to determine if lung function is normal or abnormal. Only the greatest FEV1 and FVC values will be used for this. All others will be ignored.

Abnormal results indicate one of three possible breathing patterns: obstructive, restrictive, or a combination of both.

Obstructive Disease

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, height, and weight.

Put another way, obstructive lung disease is one in which damage to the lungs and the narrowing of the airways make it harder to exhale and empty the lungs of air completely. An obstructive pattern is seen in lung conditions such as COPD and asthma.

The FEV1 values are broken down as follows:

  • FEV1 greater than 80% of predicted is normal
  • FEV1 60 percent to 79% of predicted indicates mild obstruction
  • FEV1 40 percent to 59% of predicted indicates moderate obstruction
  • FEV1 less than 40% of predicted indicates severe obstruction

Because your FEV1 is low with obstructive disease, the ratio of FEV1 to FVC (FEV1/FVC ratio) will be also lower than average.

Restrictive Disease

A restrictive lung problem means that 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 themselves.

Restrictive lung disease is sometimes associated with chest surgery, obesity, scoliosis (abnormal curvature of the spine), sarcoidosis (an inflammatory disease cause abnormal growths in tissue), and scleroderma (the abnormal buildup of unprovoked scar tissue).

A restrictive pattern will be indicated by a low FVC but a normal FEV1/FVC ratio (meaning that both values are proportionately decreased).

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 and asthma or sarcoidosis in people 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.

If you undergo a second round of spirometry testing using a bronchodilator and your values improved by 12% or more, your doctor can confidently conclude that you have asthma.

Follow-Up

If your spirometry test results are unable to provide a definitive diagnosis or determine if an obstructive and/or restrictive lung disease is involved, your doctor may order other PFTs, such as plethysmography to measure your total lung capacity.

If a definitive diagnosis can be offered, the next step would be to address treatment options and, in some cases, undergo additional tests to characterize and stage the disease. This is especially true with cancer, which may require a lung biopsy to identify the cancer cell type, imaging studies to determine the extent and stage of the disease, and genetic tests to establish if you are eligible for certain immunotherapies.

Other lung diseases may require similar secondary investigations.

Home Spirometry

A home spirometry unit—basically is a scaled-down version of the type used in clinical settings—can be useful under certain conditions with the oversight of a doctor.

A home device allows you to regularly monitor trends in your breathing patterns over a period of time to report back to your doctor. This information may help your doctor to fine-tune your treatment more precisely than with a single office visit.

(Note that there is a simpler type of spirometer called an incentive spirometer that does not provide measurements of lung function. It's a device designed to help keep a person's lung clear after surgery.)

There are certain conditions for which your doctor may recommend home monitoring. For example, a 2017 study from Iran suggested that home spirometry may be used in monitoring for complications following lung transplant surgery.

A similar 2013 study published in Contemporary Clinical Trials found that home spirometry can help detect early declines in lung function in people with cystic fibrosis, allowing for earlier treatment, a reduction in illness, slower decline in lung function, and improved quality of life.

On the downside, the accuracy of home spirometry units can vary by brand. Cheaper ones tend to be less accurate, while recommended ones can often be unaffordable. Some doctors also worry that the units may be used as substitutes for regular medical visits or encourage people to alter their treatment based on arbitrary readings.

Only use a home spirometer if your doctor recommends it. Make sure that you understand how to use it correctly and to follow your doctor's instructions regarding the accurate reporting of results.

Your doctor can also recommend the unit best suited to your condition. Home spirometers are sometimes covered by insurance, at least in part, if medically indicated.

A Word From Verywell

If you have undergone a spirometry test, have your doctor explain the findings to you, what the numbers mean, and if there have been any changes in value since your last visit. Educating yourself and being your own advocate place you in the best position to make informed choices about your health and treatment options.

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