If your doctor has recommended a spirometry test, or if you have been dealing with breathlessness, a persistent cough, or unexplained reduced exercise tolerance, spirometry is often the first and most important step in understanding what your lungs are actually doing.
At Gwinnett Pulmonary & Sleep, our board-certified pulmonologists and respiratory therapists have been performing and interpreting spirometry for patients across Gwinnett County since 1983. The test is quick, painless, and available at all five of our office locations, and the information it provides can be the difference between years of undiagnosed lung disease and a clear path to treatment.
What Is Spirometry?
Spirometry is the most widely performed lung function test in respiratory medicine. It measures how much air you can exhale and how quickly, producing objective, quantifiable data about your airway function that symptoms and physical examination alone cannot provide.
The test uses a device called a spirometer, connected to a mouthpiece you breathe into. You take the deepest possible breath and then exhale as forcefully and completely as you can. The spirometer records the volume and speed of that exhalation, generating two primary measurements that form the foundation of most pulmonary diagnoses:
Forced Vital Capacity
The total volume of air exhaled during a full, forceful exhalation after a maximum inhalation. A reduced FVC indicates that the lungs are not holding as much air as expected — a pattern associated with restrictive lung conditions.
Forced Expiratory Volume in One Second
The volume of air exhaled in the first second of that forceful exhalation. FEV1 reflects how quickly air can move out of the lungs and is the primary marker of airway obstruction.
FEV1/FVC Ratio
The relationship between these two values is the most diagnostically important spirometry output. A reduced ratio, where FEV1 is disproportionately low relative to FVC, indicates obstructive lung disease. A preserved or elevated ratio with reduced FVC suggests restriction.
What Does Spirometry Test For?
Spirometry is used to detect, confirm, and monitor a wide range of respiratory conditions:
Asthma. Spirometry is central to asthma diagnosis and management. In asthmatic patients, FEV1 is typically reduced during symptomatic periods, and a significant improvement following bronchodilator administration, defined as a 12% or greater increase and at least 200 mL, confirms reversible airway obstruction, the hallmark of asthma. Serial spirometry over time tracks whether asthma is well controlled or worsening.
COPD. Spirometry is the definitive diagnostic test for chronic obstructive pulmonary disease. A post-bronchodilator FEV1/FVC ratio below 0.70 confirms airflow obstruction consistent with COPD, and the degree of FEV1 reduction determines disease severity, from mild (GOLD Stage 1) through very severe (GOLD Stage 4). Without spirometry, COPD cannot be formally diagnosed or staged.
Pulmonary fibrosis and restrictive lung disease. A reduced FVC with a preserved or elevated FEV1/FVC ratio suggests a restrictive pattern; the lungs are not filling fully. This pattern is associated with interstitial lung diseases such as pulmonary fibrosis, as well as chest wall conditions and neuromuscular diseases affecting respiratory muscle function.
Pre-surgical evaluation. Spirometry establishes baseline lung function before thoracic procedures or other surgeries where pulmonary reserve is a relevant risk factor.
Occupational and environmental lung disease. Exposure to asbestos, coal dust, silica, chemical fumes, and other inhaled toxins can cause measurable spirometric changes. Spirometry is used to detect and monitor these effects.
Monitoring treatment response. For patients already diagnosed with a lung condition, repeat spirometry over time tracks whether the condition is progressing, stable, or improving in response to treatment.
How to Prepare for a Spirometry Test
Accurate spirometry results depend significantly on how you prepare. The most common causes of inaccurate or uninterpretable results are avoidable:
- Do not smoke for at least four to six hours before the test. Smoking causes acute airway changes that will alter your results
- Avoid caffeine and alcohol on the day of testing, as both can affect airway tone
- Do not eat a heavy meal for several hours before your appointment; a full stomach restricts diaphragm movement and reduces measured lung volumes
- Hold short-acting bronchodilators, such as albuterol, for 4 to 6 hours before testing unless your provider instructs otherwise. Long-acting bronchodilators should typically be withheld for 12 to 24 hours. Always confirm with your care team
- Wear loose, comfortable clothing that does not restrict chest expansion
- Inform our team if you have had a recent respiratory infection; active illness can temporarily alter spirometry results, and testing may need to be rescheduled
If you have specific questions about your preparation instructions, contact our office before your appointment.
What Happens During a Spirometry Test?
The test is performed in our office by a trained respiratory therapist and takes between 15 and 30 minutes from start to finish.
You will be seated comfortably and fitted with a soft nose clip to ensure all airflow passes through the mouthpiece. The respiratory therapist will explain each step before you begin and coach you through the maneuvers to ensure the best possible effort and consistent results.
For each attempt, you will breathe in as deeply as possible, filling your lungs completely, and then exhale as hard and fast as you can into the mouthpiece, continuing to push air out until your lungs are empty. The maneuver requires genuine effort; your respiratory therapist will encourage you through each exhalation to ensure maximum output.
The test is typically repeated two to three times to ensure reproducibility. Consistent results across attempts confirm that the measurements are accurate and reliable. If bronchodilator response testing is included, you will be given an inhaled bronchodilator after the initial measurements and spirometry will be repeated 15 to 20 minutes later.
Some patients feel briefly lightheaded after the forceful exhalations; this is normal and passes quickly.
Understanding Your Spirometry Test Results
Results are reported as measured values and as a percentage of the predicted normal value for someone of your age, sex, height, and ethnicity. This percentage-predicted framework is how your pulmonologist determines whether your lung function is within the normal range or significantly reduced.
Normal Spirometry Values by Age
Normal predicted values decline gradually with age after early adulthood; peak lung function is typically reached in the mid-twenties and decreases slowly thereafter. This natural decline is factored into the reference equations used to calculate your predicted values, meaning your results are always compared against age-appropriate norms rather than a single universal standard.
A result at or above 80% of the predicted value is generally considered within the normal range for both FVC and FEV1. An FEV1/FVC ratio above 0.70 in adults is considered normal, though lower limits of normal calculated from reference equations are increasingly used in clinical practice.
Interpreting the Pattern
Obstructive pattern — A reduced FEV1/FVC ratio with relatively preserved FVC indicates that airflow out of the lungs is impaired. This pattern is characteristic of asthma, COPD, and bronchiectasis. The severity of obstruction is graded by how far FEV1 falls below predicted.
Restrictive pattern — A reduced FVC with a normal or elevated FEV1/FVC ratio suggests the lungs are not filling fully. True restriction is confirmed by lung volume testing showing reduced total lung capacity. This pattern is associated with pulmonary fibrosis, pleural disease, chest wall restriction, and neuromuscular conditions.
Mixed pattern — Elements of both obstruction and restriction may be present simultaneously, as in combined pulmonary fibrosis and emphysema or severe COPD with concurrent restriction.
Normal spirometry — A normal result does not always rule out lung disease. Some conditions, including early pulmonary fibrosis, pulmonary vascular disease, and mild asthma outside of symptomatic periods, may produce normal spirometry. Your pulmonologist interprets the results alongside your symptoms, history, and other test results.
Results are reviewed with you by your pulmonologist, who will explain the findings in plain language and outline recommended next steps.
Schedule Your Spirometry Test in Gwinnett County
Whether you have been referred for spirometry, are managing a known lung condition, or have symptoms that need evaluation, our team is ready to help. At Gwinnett Pulmonary & Sleep, we combine precise testing technique with expert clinical interpretation to give you clear, actionable information about your lung health.
Call our office to schedule an appointment, or request one online.
Spirometry is available at all five of our Gwinnett County offices: Lawrenceville, Duluth, Snellville, Dacula, and Suwanee, with appointments typically available within a short wait.
Frequently Asked Questions
What does a spirometry test for?
Spirometry is used to diagnose and monitor asthma, COPD, pulmonary fibrosis, and other obstructive and restrictive lung conditions. It is also used for pre-surgical evaluation, monitoring the effects of occupational exposures, and tracking treatment response over time.
How long does a spirometry test take?
The test itself takes approximately 15 to 30 minutes, including preparation, the breathing maneuvers, and any rest periods between attempts. If bronchodilator response testing is included, allow an additional 20 to 30 minutes for the medication to take effect before repeat measurements.
What do spirometry test results mean?
A reduced FEV1/FVC ratio indicates obstructive lung disease; airflow out of the lungs is impaired, as seen in asthma and COPD. A reduced FVC with a preserved FEV1/FVC ratio suggests restriction; the lungs do not fill fully, as seen in pulmonary fibrosis. Your pulmonologist will explain your specific results and what they mean for your diagnosis and treatment.
Is spirometry used to diagnose asthma?
Yes. Spirometry combined with bronchodilator response testing is the standard approach for confirming asthma. A significant improvement in FEV1 after bronchodilator use, 12% or more and at least 200 mL, confirms reversible airway obstruction consistent with asthma. FENO testing may also be used alongside spirometry to assess airway inflammation.
How much does a spirometry test cost?
Spirometry is covered by Medicare and most private insurance plans when ordered with a supporting clinical indication. Out-of-pocket costs vary depending on your coverage and deductible. Our team can confirm your benefits and answer billing questions before your appointment.
Do I need to stop my inhalers before spirometry?
In most cases, yes, short-acting bronchodilators such as albuterol should be withheld for four to six hours before testing, and long-acting bronchodilators for 12 to 24 hours. However, always confirm with your provider, as specific instructions may vary depending on the purpose of your test.