Breathing problems are often invisible on the outside, but measurable from within. If you’ve been experiencing persistent shortness of breath, a chronic cough, or unexplained exercise intolerance, pulmonary function testing provides your physician with objective, quantifiable data on how your lungs are actually performing. Not an estimate. Not a general impression. Measured values that point toward a diagnosis.
At Gwinnett Pulmonary & Sleep, our board-certified pulmonologists have been performing lung function testing for patients across Gwinnett County since 1983. We offer a full suite of pulmonary function tests, from spirometry and diffusion capacity testing to FENO asthma testing, pulse oximetry, and the six-minute walk test, all available at our five conveniently located offices.
What Is a Pulmonary Function Test?
A pulmonary function test, commonly referred to as a PFT, is a non-invasive breathing evaluation that measures how well your lungs take in air, move air in and out, and transfer oxygen into the bloodstream. PFTs are painless, do not require sedation, and are typically completed within a single office visit.
The results provide your pulmonologist with a detailed picture of your lung mechanics, including lung capacity, airflow rate, and gas exchange efficiency, that cannot be obtained through imaging alone. This information is used to diagnose respiratory conditions, monitor disease progression, evaluate the effectiveness of current treatments, and determine whether lung function has been affected by occupational exposures or other environmental factors.
What Do Pulmonary Function Tests Measure?
Depending on your symptoms and clinical history, your provider may order one or several of the following tests:
- Spirometry measures how much air you can exhale and how quickly. It produces two key values: forced vital capacity (FVC) — the total volume of air expelled in a full exhalation — and forced expiratory volume in one second (FEV1), the amount exhaled in the first second. The ratio between these two values is central to diagnosing and classifying obstructive and restrictive lung conditions.
- Lung volume testing measures the total amount of air your lungs can hold, including residual volume, the air that remains in the lungs after a full exhalation. This measurement helps distinguish between obstructive conditions, in which air becomes trapped, and restrictive conditions, in which the lungs cannot fully expand.
- Diffusion capacity (DLCO) measures how efficiently oxygen crosses from the air sacs in your lungs into the bloodstream. A reduced DLCO can indicate pulmonary fibrosis, emphysema, pulmonary hypertension, or other conditions that impair gas exchange at the alveolar level.
- Bronchodilator response testing is often performed alongside spirometry. A bronchodilator medication is administered via inhaler, and spirometry is repeated after 15 to 20 minutes. An improvement in FEV1 following bronchodilator use is a diagnostic indicator of reversible airway obstruction, a hallmark of asthma.
When Is a Pulmonary Function Test Required?
Your provider may recommend pulmonary function testing if you are experiencing symptoms suggestive of a respiratory condition or have a known diagnosis that requires monitoring. Common reasons for referral include:
- Shortness of breath during activity or at rest that has not been explained by cardiac evaluation or other workup
- Chronic or persistent cough lasting eight weeks or more, particularly when other causes have been ruled out
- Wheezing or chest tightness that occurs regularly or worsens with exercise or cold air exposure
- A confirmed or suspected diagnosis of asthma, COPD, pulmonary fibrosis, bronchiectasis, or sarcoidosis
- Monitoring known lung disease to track progression and evaluate treatment response over time
- Pre-surgical evaluation when a procedure carries respiratory risk and baseline lung function needs to be established
- Occupational or environmental exposure to dust, chemicals, asbestos, or other inhaled toxins that may have affected lung tissue
- Unexplained decline in exercise tolerance or oxygen levels during physical activity
If you are unsure whether pulmonary function testing is appropriate for your symptoms, our team can evaluate your history and advise during a consultation.
Related Lung Function Tests
Pulmonary function testing extends beyond the core PFT battery. Depending on your clinical needs, your provider may also recommend one or more of the following evaluations, all available at Gwinnett Pulmonary & Sleep:
- FENO Asthma Testing → Measures the level of nitric oxide in exhaled breath as a marker of eosinophilic airway inflammation. Used to confirm asthma, assess inflammation control, and guide decisions about inhaled corticosteroids and biologic therapy.
- Pulse Oximetry Testing → Measures oxygen saturation levels in the blood at rest, during exercise, and overnight. Used to assess oxygenation, evaluate the need for supplemental oxygen, and re-qualify Medicare patients for home oxygen therapy.
- Six Minute Walk Test → Measures functional exercise capacity by tracking walking distance and oxygen saturation over six minutes. Commonly used for patients with COPD, pulmonary fibrosis, and pulmonary hypertension to assess disease severity and treatment response.
- Spirometry → The most widely performed lung function test, measuring airflow to detect and monitor obstructive and restrictive conditions. Available at all five Gwinnett Pulmonary & Sleep locations.
What to Expect Before Your Pulmonary Function Test
Getting accurate results from pulmonary function testing depends significantly on how you prepare. The most common reasons for inaccurate or uninterpretable results are avoidable with the right preparation.
Before your appointment:
- Do not smoke for at least four to six hours prior to testing. Smoking causes acute airway changes that will artificially alter your results.
- Eat a light meal and avoid heavy food for several hours before the test. A full stomach restricts diaphragm movement and can reduce your measured lung volumes.
- Avoid caffeine and alcohol on the day of testing, as both can affect airway tone and breathing patterns.
- Hold bronchodilator inhalers unless otherwise instructed by your provider. Short-acting bronchodilators such as albuterol should typically be withheld for four to six hours; long-acting bronchodilators for 12 to 24 hours. Always confirm with your care team.
- Wear comfortable, non-restrictive clothing that does not limit chest expansion or deep breathing.
- Inform your provider of any recent respiratory illness, as an active infection can temporarily alter results and may require rescheduling.
If you have questions about your specific preparation instructions, contact our office before your appointment. Arriving prepared ensures your results are accurate and actionable.
How Pulmonary Function Testing Works
PFTs are performed in our office by trained respiratory therapists. The testing environment is calm, and you will have time to rest between measurements.
For spirometry, you will be seated and fitted with a soft nose clip. You will breathe normally for a few cycles, then inhale as deeply as possible and exhale as forcefully and completely as you can into a mouthpiece connected to the spirometer. This effort is typically repeated two to three times to ensure consistent, reproducible results.
Lung volume testing uses a technique called body plethysmography or gas dilution, depending on which method your provider orders. You breathe through a mouthpiece in a sealed chamber or through a series of timed breathing maneuvers with a specific gas mixture.
Diffusion capacity testing requires a single deep inhalation of a trace amount of carbon monoxide gas, followed by a brief breath hold, and then a slow exhalation. The difference between the amount inhaled and exhaled reflects how efficiently your lungs transfer gas into the blood.
PFTs are painless. Some patients feel slightly lightheaded after forceful breathing, which is normal and passes quickly.
Understanding Your Pulmonary Function Test Results
Results are expressed as measured values compared against predicted normal values for your age, sex, height, and ethnicity, a framework called percent predicted. A result at or above 80% predicted is generally considered within the normal range, though your pulmonologist interprets results in the context of your full clinical picture.
- Obstructive pattern: A reduced FEV1/FVC ratio indicates obstruction, air leaving the lungs more slowly than expected. This pattern is characteristic of asthma, COPD, and bronchiectasis.
- Restrictive pattern: A reduced FVC with a normal or elevated FEV1/FVC ratio suggests restriction; the lungs are not filling to their full capacity. This can indicate pulmonary fibrosis, chest wall disease, or neuromuscular conditions affecting the respiratory muscles.
- Mixed pattern: Some patients show elements of both obstruction and restriction, which may point to conditions such as combined pulmonary fibrosis and emphysema (CPFE) or severe COPD with concurrent restriction.
- Normal values by age: Predicted normal values account for age, as lung function naturally declines gradually after peak respiratory capacity is reached in early adulthood. Your provider will compare your results against age-appropriate reference values and explain what the findings mean in the context of your symptoms and history.
Results are reviewed with you by your pulmonologist, who will explain the findings in plain language and outline the recommended next steps.
Schedule Pulmonary Function Testing in Gwinnett County
If you have been referred for pulmonary function testing or are experiencing respiratory symptoms that need evaluation, our team is ready to help. At Gwinnett Pulmonary & Sleep, we combine precise testing with expert clinical interpretation to give you clear answers about your lung health.
Call our office to schedule an appointment, or request one online.
Pulmonary function testing is available at all five of our offices: Lawrenceville, Duluth, Snellville, Dacula, and Suwanee, with appointments typically available within a short wait.
Frequently Asked Questions
What does a pulmonary function test reveal about your breathing?
PFTs reveal how much air your lungs can hold, how quickly you can exhale, and how efficiently oxygen crosses from your lungs into your blood. Together, these measurements can identify obstructive patterns, where airflow out of the lungs is impaired; restrictive patterns, where the lungs cannot fully expand; and gas exchange abnormalities that point to specific conditions.
What is FVC in a pulmonary function test?
FVC stands for forced vital capacity, the total volume of air you can forcefully exhale after taking the deepest breath possible. It is one of the two primary spirometric measurements, alongside FEV1. A reduced FVC can indicate a restrictive lung condition, while the FEV1/FVC ratio is used to identify obstruction.
When is a pulmonary function test required?
PFTs are typically ordered when a patient has unexplained shortness of breath, a persistent cough, wheezing, or a suspected or confirmed respiratory condition. They are also used for pre-surgical evaluation, monitoring of known lung disease, and assessment of occupational or environmental lung damage.
What should I not do before a pulmonary function test?
Avoid smoking for at least four to six hours beforehand. Do not eat a heavy meal, consume caffeine or alcohol, or take bronchodilator inhalers unless your provider has specifically told you to continue them. Wear loose, comfortable clothing. If you have an active respiratory infection, contact our office as your appointment may need to be rescheduled.
How long does a pulmonary function test take?
A standard PFT appointment typically takes between 45 minutes and 1 hour, including preparation, testing, and rest periods between maneuvers. If additional tests such as bronchodilator response testing are included, the appointment may run slightly longer. Your care team will give you a time estimate when you schedule.
What are normal pulmonary function test values by age?
Normal values are expressed as a percentage of predicted values based on your age, sex, height, and ethnicity. Results at or above 80% of predicted are generally considered within the normal range. Lung function naturally declines gradually with age after early adulthood, so age-appropriate reference values are always used when interpreting results. Your pulmonologist will explain your specific results in context during your follow-up.
Can a pulmonary function test diagnose asthma?
Yes. Spirometry combined with bronchodilator response testing is a standard tool for diagnosing asthma. A significant improvement in FEV1 after bronchodilator administration — typically defined as 12% or greater and 200 mL or more — supports a diagnosis of reversible airway obstruction consistent with asthma. FENO testing can also be used alongside PFTs to assess the type and degree of airway inflammation.
How do I understand my pulmonary function test results?
Your pulmonologist will review your results with you and explain what the values mean in the context of your symptoms and history. In general, an obstructive pattern with a reduced FEV1/FVC ratio suggests conditions like asthma or COPD. A restrictive pattern, reduced FVC with preserved ratio, can indicate pulmonary fibrosis or other conditions limiting lung expansion. Your provider will outline the recommended next steps based on findings.
Are pulmonary function tests covered by insurance?
PFTs are covered by Medicare and most private insurance plans when ordered by a physician with a supporting clinical indication. Our team can confirm your coverage and answer billing questions before your appointment.