Spirometry is a lung-function test that measures how much air you can forcefully breathe out and how quickly you can exhale it. It may be considered when investigating persistent cough, wheezing, breathlessness, or suspected conditions such as asthma or COPD. Results need to be interpreted alongside symptoms, medical history and clinical assessment rather than used for self-diagnosis.
Key Takeaways
- Spirometry measures airflow and the amount of air you can forcibly exhale
- FEV1, FVC and the FEV1/FVC ratio are the key measurements
- Several breathing attempts are usually needed for a reliable result
- The test may be repeated after a bronchodilator inhaler
- Results should always be interpreted alongside symptoms and clinical assessment
Why Might a GP Recommend a Spirometry Test?
A GP may consider or arrange spirometry when a patient has persistent or recurring breathing symptoms that need further assessment.
Common reasons include:
- Persistent cough that has not resolved
- Recurrent wheezing
- Unexplained breathlessness or reduced exercise tolerance
- Chest tightness
- Assessment for suspected asthma
- Assessment for suspected COPD, particularly in current or former smokers
- Monitoring established respiratory conditions where appropriate
Australian asthma guidance recommends spirometry when investigating suspected asthma in adults and adolescents. Spirometry is also an essential part of assessing and confirming COPD when it is clinically suspected.
If breathing symptoms keep returning or are affecting daily activity, a general medicine GP consultation at Huntlee Healthcare can help assess what may be contributing and whether spirometry or another investigation is appropriate.
How Should You Prepare for Spirometry?
Preparation is straightforward, but following specific instructions from the clinic or testing service matters.
Before the test, it may help to:
- Follow any instructions provided by the clinic or respiratory laboratory.
- Tell the clinician which inhalers and medicines you currently take.
- Wear comfortable clothing that does not restrict deep breathing.
- Let the clinician know if you are unwell, have had a recent respiratory infection, or have any other significant health concern.
For some diagnostic testing, specific bronchodilators may need to be withheld beforehand. Do not stop any prescribed inhaler or medicine on your own. Wait for individual instructions from your clinician or testing service.
What Happens During a Spirometry Test?
The test involves a series of forceful breathing efforts into a device called a spirometer. Spirometry does not usually cause pain, although repeated forceful breathing can feel tiring or uncomfortable for some people.
The general sequence is:
- Sit upright and receive instructions from the operator
- Take the deepest breath possible
- Seal your lips tightly around the mouthpiece
- Blow out as hard and as fast as you can
- Continue blowing until you are asked to stop
- Repeat the manoeuvre several times
A nose clip may be used depending on the testing technique. National Asthma Council guidance recommends at least three technically acceptable efforts so the clinician can assess whether results are consistent and reliable.
Being asked to repeat the test does not mean you have performed it incorrectly. Several consistent efforts help produce a more reliable measurement.
What Do FEV1, FVC and the FEV1/FVC Ratio Mean?
These three measurements are the core outputs of a spirometry test.
| Measurement | Plain-English meaning |
| FEV1 | How much air you can forcefully breathe out in the first second |
| FVC | The total amount of air you can forcefully breathe out after a full breath in |
| FEV1/FVC ratio | The proportion of the full forced breath that comes out in the first second |
Australian Asthma Handbook guidance states that a reduced FEV1 can indicate abnormal lung function, while a reduced FEV1/FVC ratio indicates expiratory airflow obstruction.
A reduced ratio shows that airflow is limited, but it does not by itself identify the cause. Results are interpreted against reference values based on individual factors such as age, height and sex, not a single universal percentage.
The Australian Asthma Handbook’s lung function testing guidance explains how spirometry measurements are used when investigating asthma and other respiratory conditions.
Why Is Spirometry Sometimes Repeated After an Inhaler?
Some spirometry tests are repeated after a bronchodilator medicine, which is a short-acting inhaled medicine that helps open the airways.
The clinician compares measurements before and after to see whether airflow improves following the bronchodilator. This is called bronchodilator responsiveness testing. Australian asthma guidance recommends it as part of diagnostic spirometry when asthma is being investigated because demonstrating variable airflow limitation can support the assessment.
Improvement after a bronchodilator does not automatically confirm asthma, and a lack of improvement does not rule it out. The full clinical picture is always considered alongside the numbers.
What Can Spirometry Results Show?
Depending on the pattern of results, spirometry may provide information about:
- Whether airflow appears reduced compared with expected values
- Whether an obstructive airflow pattern is present
- Whether airflow changes significantly after a bronchodilator
- How lung function compares over time when repeat testing is used for monitoring
Spirometry is central to assessing both asthma and COPD, but the clinical meaning of a result differs between conditions. For patients with established asthma or COPD, ongoing chronic disease management may include periodic lung-function monitoring as part of their overall care.
Spirometry measures lung function. It does not replace the clinical assessment needed to determine why a result is abnormal or what treatment may be appropriate.
Can Spirometry Be Normal if You Still Have Breathing Symptoms?
Yes. Normal spirometry does not automatically rule out every respiratory condition.
Asthma in particular can produce variable symptoms. If testing is performed when symptoms are absent or mild, spirometry may appear normal even in someone with asthma. Australian Asthma Handbook guidance explicitly states that normal spirometry does not exclude asthma.
If symptoms remain concerning despite a normal result, a GP may consider repeat spirometry, additional lung function tests, or referral for specialist respiratory assessment, depending on the clinical picture.
What Happens After the Test?
The GP or referring clinician reviews the test quality and measurements together with:
- Your symptoms and how long they have been present
- Medical history and medicines
- Smoking or occupational exposure history
- Physical examination findings
Further testing or respiratory referral may be considered when results do not fully explain symptoms or when the clinical question remains unclear.
When Should You Speak With a GP?
Persistent cough, wheezing or breathlessness is worth discussing with a GP, particularly when symptoms keep returning, affect normal activity, or have gradually worsened over time. A GP can assess the broader picture and discuss whether spirometry or another respiratory assessment may be appropriate for your individual circumstances.
For patients in Huntlee and North Rothbury with ongoing breathing symptoms, booking a GP appointment at Huntlee Healthcare is a practical first step toward understanding what may be contributing.
FAQs
Does a spirometry test hurt?
No painful procedure is involved, but forceful repeated breathing can be tiring, and some people may briefly cough or feel mildly light-headed after the test.
What does a low FEV1 mean?
A low FEV1 means the amount of air breathed out in the first second is lower than expected. On its own, it does not identify the cause and needs to be interpreted alongside FVC, the FEV1/FVC ratio, test quality and the broader clinical picture.
Can spirometry diagnose asthma?
Spirometry can provide objective evidence supporting an asthma assessment, particularly when variable airflow limitation is demonstrated, but more than one test or further assessment may sometimes be needed.
Can spirometry diagnose COPD?
Post-bronchodilator spirometry is essential for confirming persistent airflow limitation when COPD is suspected, but symptoms, exposure history, and clinical context are also considered alongside the measurements.
Sources and further reading
Australian Asthma Handbook — Lung Function Tests
National Asthma Council Australia — Spirometry Handbook for Primary Care
Lung Foundation Australia — Lung Function Tests
Australian Commission on Safety and Quality in Health Care — COPD Clinical Care Standard