A COPD lung function test is most often spirometry. You take a deep breath, blow out as hard and as long as you can into a tube, and a small machine measures the air. As of October 2026, a PubMed abstract on COPD lung function tests says COPD diagnosis relies on chronic airflow limitation that is poorly reversible or not reversible, defined by an FEV1/FVC ratio below 70%, and a clinician puts that result together with symptoms and other tests.
FEV1 is how much air you blow out in the first second, and FVC is the total you blow out. A low ratio means air is leaving your lungs more slowly than it should. That single ratio is the center of the test, but the full picture usually includes a few more checks, and this guide walks through each one. The research behind it comes from that PubMed abstract and from BMJ Best Practice, a clinical reference that cites the 2026 GOLD report.
What is diagnostic spirometry used for?
Spirometry is the main breathing test for COPD. The Zephyr Valve maker’s own COPD diagnosis page says spirometry “measures lung function and capacity,” and that its results “help determine what type of lung disease you have and how severe it is.” As of October 2026, BMJ Best Practice’s COPD tests page says the ratio of FEV1 to FVC “indicates whether airflow obstruction is present.”
The PubMed abstract adds that spirometry is needed both to diagnose COPD and to follow people over time. It stages severity by post-bronchodilator FEV1 as a percent of the predicted value: above 80% is stage I, 50 to 80% is stage II, 30 to 50% is stage III, and below 30% is stage IV. BMJ Best Practice says spirometry should be done after at least one short-acting inhaled bronchodilator, which helps reduce variability between readings.
If a test is coming up, preparing for spirometry covers what to do beforehand, and spirometry for COPD explains what the test measures and where it stops.
The common COPD tests at a glance
| Test | What it looks at | What is reported |
|---|---|---|
| Spirometry | Air blown out in the first second (FEV1) and total blown out (FVC) | A ratio below 0.7 (70%) indicates airflow obstruction; severity is staged by post-bronchodilator FEV1 (PubMed abstract; BMJ Best Practice) |
| Bronchodilator reversibility test | Spirometry before and after a bronchodilator medicine | The Zephyr Valve maker describes a baseline reading, a 15-minute wait, a bronchodilator dose, then a repeat test |
| Diffusing capacity (DLCO) | How well gas passes from the lungs into the blood | As of October 2026, BMJ Best Practice cites the 2026 GOLD report: a low DLCO (below 60% predicted) is associated with decreased exercise capacity, worse health status, and increased risk of death |
| Chest CT scan | Detailed images of lung tissue | Gives better visualization of the type and distribution of lung tissue damage and bulla formation than a chest X-ray (BMJ Best Practice) |
| Chest X-ray | A basic picture of the chest | Seldom diagnostic on its own, but useful for ruling out other problems (BMJ Best Practice) |
| Pulse oximetry | Oxygen level in the blood, measured with a clip | BMJ Best Practice says an oxygen saturation of 88% to 90% may be acceptable in chronic disease; 92% or lower means an arterial blood gas should be checked |
| Arterial blood gas | Oxygen and carbon dioxide in blood drawn from an artery | Checked in people who are acutely sick, with FEV1 below 35% predicted, or with signs of respiratory failure (BMJ Best Practice) |
| Exercise or six-minute walk test | How you handle exertion | Can help when breathlessness is out of proportion to spirometry; helps select people for rehabilitation (BMJ Best Practice) |
Is restrictive lung disease serious?
The 70% ratio is the COPD line. If your report shows a different pattern, including one people call restrictive, ask your clinician what it means for you and how serious it is in your case. Bring the printed numbers to that visit so you can go through them together.
What are the diagnostic criteria for emphysema?
The PubMed abstract does not set out separate diagnostic criteria for emphysema. It sets out criteria for COPD, built on the FEV1/FVC ratio below 70% and staged by post-bronchodilator FEV1. The Zephyr Valve maker’s page describes COPD as a disease that “destroys the lungs over time by damaging the little grape-like sacs called alveoli.” BMJ Best Practice’s example COPD chest CT is captioned “hyperinflated lung, emphysematous changes.” Ask your clinician how emphysema is assessed in your case.
Would emphysema show on a CT scan?
BMJ Best Practice says chest CT provides better visualization of the type and distribution of lung tissue damage and bulla formation than a chest X-ray, and its example COPD CT shows emphysematous changes. Ask your clinician whether CT is right for you.
As of October 2026, BMJ Best Practice, citing the 2026 GOLD report, says CT should be considered for people with persistent exacerbations, for those whose symptoms do not correspond with their lung function results, for those with FEV1 below 45% of predicted with significant hyperinflation, and for those who meet lung cancer screening criteria.
BMJ Best Practice also cites the US Preventive Services Task Force, which recommends annual low-dose CT for lung cancer screening in patients with COPD that is due to smoking. If a screening CT finds a nodule, lung nodules and lung-rads explains how those results are read.
Is there an emphysema blood test?
No blood test is listed as diagnosing emphysema. BMJ Best Practice lists blood tests as supporting tests in COPD. A complete blood count may show polycythemia, anemia, or leukocytosis. An alpha-1 antitrypsin level is tested when suspicion is high, such as a positive family history or atypical COPD in young patients under 45 and in nonsmokers. Blood eosinophil counts can identify patients who are more likely to respond to inhaled corticosteroids (ICS).
Can I do an emphysema test at home?
The PubMed abstract does not address testing for emphysema at home. The Zephyr Valve maker’s page describes spirometry this way: you “exhale as forcefully as you can into a tube,” and doctors connect the tube to “a small machine called a spirometer.” Ask your clinician whether any home device is appropriate for you, and bring any readings to your next visit so they can be compared with your test results.
What are the COPD symptoms I should watch for?
The Zephyr Valve maker lists these COPD symptoms: shortness of breath, coughing, wheezing, excess mucus production, chest tightness, fatigue, swelling in the ankles, feet, or legs, and frequent respiratory infections. Its page says diagnosing COPD early matters because prompt treatment “may help slow the progression of the disease.” If your cough has changed, smoker’s cough or copd covers when a cough is worth getting checked.
If you have sudden or severe trouble breathing, call 911 or go to the nearest emergency department now.
What are my options at an early stage?
The PubMed abstract says spirometry and flow-volume curves during forced breathing out are sufficient to assess severity at stage I. It does not show which treatment to use at that stage, so ask your clinician what follow-up they recommend based on your results.
The CDC’s smoking cessation fast facts say quitting “greatly reduces the risk of developing smoking-related diseases.” The CDC says there are seven medicines approved by the Food and Drug Administration to help you quit, and that all “have been shown to be safe and effective for adults who smoke cigarettes.” If you are pregnant, breastfeeding, or younger than 18, the CDC says you should not use these medicines without talking to your doctor. Free help is available by calling 1-800-QUIT-NOW or by texting QUITNOW to 333888. MyHealthfinder notes that “it often takes people several tries to quit smoking,” so a restart is part of the process, not a failure.
Which medicine or program fits you is a decision for you and your clinician, based on your stage, symptoms and test results.
How can I improve my lung function if I have emphysema?
Rush University’s quit-smoking tips say that within two to three months, “your lung function starts to improve.” That is general guidance for people who quit smoking. The Rush page does not address people who already have COPD or emphysema, so it does not tell you how much lung function you might regain.
Exercise testing helps select people for rehabilitation, according to BMJ Best Practice. Ask your clinician whether rehabilitation is right for you and what it would do for your breathing. Ask which changes are realistic for your results. The PubMed abstract says spirometry is required for follow-up of COPD patients, and it recommends looking at other measures too, such as the 6-minute walk test, breathlessness and body mass index. Ask your clinician how your progress will be tracked.
Are mood changes linked to COPD?
BMJ Best Practice lists an echocardiogram to assess cardiac status when heart disease or pulmonary hypertension is suspected. Whether tracking a measure like DLCO changes care is the kind of question covered in surrogate endpoints versus outcomes people feel (our research library).
Mood matters during quitting too. The CDC’s withdrawal page says that “some people feel mood changes for a short time after they quit smoking,” especially if you have had anxiety or depression before. Smokefree.gov says that some people “felt irritable, anxious, or depressed” after they quit. If feelings of depression get worse or do not get better, the CDC says to talk to your healthcare provider, call the quitline at 1-800-QUIT-NOW, or seek emergency help. You can also call or text 988, the Suicide and Crisis Lifeline, any time. For how withdrawal differs from COPD symptoms, see withdrawal or copd symptoms.
What are the treatment options side by side?
| Option | What it is | What is reported | Who it may suit | Cost to check |
|---|---|---|---|---|
| Spirometry with bronchodilator test | Breathing test using a spirometer | Diagnosis and follow-up (PubMed abstract; BMJ Best Practice) | Anyone being checked for COPD | Ask your insurer or the clinic |
| FDA-approved quit-smoking medicines | Seven medicines, including patches, gum, lozenges, and pills | “Safe and effective for adults who smoke cigarettes” (CDC) | Adults who smoke cigarettes; pregnant or breastfeeding people, and those under 18, should not use them without talking to a doctor (CDC) | Under the Affordable Care Act, most insurance plans must cover treatment to help people quit smoking (MyHealthfinder, content last updated May 1, 2025); check with your insurer |
| Bronchodilator medicines | Medicines that help open your airways (Zephyr Valve maker’s description) | Used in the reversibility test; BMJ Best Practice says spirometry should follow at least one short-acting inhaled bronchodilator | Ask your clinician whether one fits you | Ask your pharmacy and insurer |
| Rehabilitation | Rehabilitation, which exercise testing helps select people for | Exercise testing helps select patients for rehabilitation (BMJ Best Practice) | People your clinician selects after an exercise test | Ask the clinic that runs it |
| Zephyr Valve | A valve placed in the airways by bronchoscopy, which the maker says requires no incisions | The maker says: “If you’re diagnosed with severe COPD/emphysema, the Zephyr ® Valve may be an option for you,” and that it is “not another medication or surgery” | The maker says severe COPD or emphysema | Ask the treating center and your insurer |
The Zephyr Valve is made by Pulmonx. The maker’s page says its physician locator includes doctors who completed the company’s training, and that “the physicians do not pay or receive a fee for inclusion on this list,” though “some physicians on this list may provide consulting services to the company.” The same page lists that an assessment center must have access to body plethysmography and high-resolution CT. The Zephyr Valve details here are the maker’s own claims.
What should I bring to my appointment?
- Ask which test they want, and why, based on your symptoms.
- Ask for your FEV1, FVC and FEV1/FVC numbers, and which stage they place you in.
- Ask whether a CT scan or a DLCO test is needed for you.
- Ask what a restrictive pattern on your report would mean, if you see one.
- Ask about quit-smoking support and whether your insurance covers it.
- Ask what any treatment would cost you before you agree to it.
Start with one call: book the breathing test, or ask your clinic for copies of your last results. A clear set of numbers makes every next step easier.
By SmokersLung.com Respiratory Health Education Team