If a GP has recommended a spirometry test, or if you have an ongoing cough, wheeze or breathlessness and want to understand how lung function is assessed, this article explains what to expect. Spirometry is a lung function test that measures how much air you can forcefully breathe out and how quickly you can exhale it. It is commonly used when asthma, COPD or another airflow condition is being considered.
Key Takeaways
- Spirometry measures the amount and speed of air you can forcefully exhale
- Key measurements include FEV1, FVC and the FEV1/FVC ratio
- The test usually requires several repeated breathing efforts to get reliable results
- A bronchodilator may sometimes be given before the test is repeated
- Results are interpreted alongside symptoms, medical history and clinical findings
- Normal spirometry does not automatically rule out every respiratory condition
What Is a Spirometry Test?
Spirometry is a type of lung function test performed using a device called a spirometer. You breathe into a mouthpiece, and the machine records how much air you exhale and how fast you can exhale it.
The National Asthma Council Australia describes spirometry as an important objective lung function test used to assess airflow and support respiratory assessment in primary care. It is non-invasive and does not involve needles, though the repeated forceful breathing can feel tiring.
Why Might a GP Recommend Spirometry?
A GP does not recommend spirometry for every patient with a cough or cold. The decision depends on symptoms, history and clinical judgement.
A GP may suggest spirometry when you have:
- Persistent or recurring cough
- Wheezing
- Shortness of breath or breathlessness
- Reduced ability to exercise
- Suspected asthma or COPD
- A relevant smoking or occupational-exposure history
- An existing respiratory condition that needs monitoring
A general GP consultation is the appropriate first step to assess whether spirometry or another investigation may be clinically appropriate.
If you have an ongoing cough, wheeze or breathlessness, a GP can review your symptoms and discuss whether spirometry or another investigation may be appropriate.
How Should You Prepare for the Test?
Preparation may vary depending on why the test has been recommended. Follow the specific instructions given by your clinic.
General guidance includes:
- Tell the clinician about any inhalers or respiratory medicines you use
- Do not stop prescribed medicines unless your clinic has specifically told you to
- Wear loose, comfortable clothing that allows easy breathing
- Let the clinic know if you are unwell, have a respiratory infection, or are having a flare-up of symptoms
Do not apply a fixed rule about inhalers before testing. The guidance depends on your medicine and the reason for the test.
What Happens During a Spirometry Test?
The test requires effort and co-operation. The clinician will explain what to do before you begin.
The procedure generally follows these steps:
- You sit or stand as instructed, and a nose clip may be applied
- You take the deepest breath possible
- You seal your lips firmly around the mouthpiece
- You exhale as hard and as fast and for as long as you can
- The manoeuvre is repeated several times
Multiple attempts are needed because spirometry is effort-dependent. The test is usually repeated at least three times, and additional attempts may sometimes be needed to obtain acceptable, repeatable results. Repeating the test does not mean something is wrong; it helps the clinician obtain reliable measurements. Repeating the test is not a sign that something is wrong. It is how accurate measurements are obtained.
The forceful breathing can feel tiring. Some people briefly feel light-headed or cough during or after the test.
Why Might the Test Be Repeated After an Inhaler?
In some situations, you may be given a bronchodilator inhaler and asked to repeat the test after a short wait.
This is called bronchodilator-responsiveness testing. The clinician compares measurements before and after the inhaler to assess whether airflow improves. Australian asthma guidance recommends this type of testing when assessing suspected asthma.
A significant improvement after the bronchodilator may support a pattern consistent with reversible airflow limitation. Still, the result is interpreted alongside symptoms and history, not used as a diagnosis on its own.
What Do FEV1, FVC and the FEV1/FVC Ratio Mean?
These are the three main measurements your GP will review.
FEV1
FEV1 is the amount of air you can blow out in the first second of the test. It reflects how freely air moves through the airways.
FVC
FVC is the total amount of air you can forcefully breathe out after taking a full, deep breath.
FEV1/FVC Ratio
This compares air exhaled in the first second with the total forced breath. A reduced ratio may indicate that airflow is obstructed.
Your GP interprets these figures alongside your age, height, sex, smoking history, symptoms, and the quality of the test effort. These measurements are compared with expected reference values rather than assessed as fixed universal numbers.
What Can Spirometry Results Show – and What Cannot They Show?
Spirometry may help identify:
- Whether expiratory airflow is reduced
- An obstructive airflow pattern, which can occur in asthma, COPD and other respiratory conditions.
- Whether airflow improves after a bronchodilator
- How lung function changes over time during treatment or monitoring
Spirometry cannot by itself:
- Diagnose every respiratory condition
- Rule out asthma when symptoms are absent at testing
- Confirm a restrictive lung disorder that requires additional lung-volume testing
- Replace a full clinical assessment
A normal spirometry result does not automatically exclude asthma. Australian asthma guidance states that spirometry can be normal in someone with asthma, particularly when symptoms are not present at the time of the test.
What Happens After the Test?
The clinician reviews the test quality and the results before drawing any conclusions.
Depending on the findings, follow-up may include:
- A discussion of what the results suggest in the context of your symptoms
- Repeat spirometry at a later date
- Additional respiratory investigations
- Treatment review or initiation where indicated
- Referral to a respiratory specialist if needed
For patients with established asthma or COPD, spirometry may also be part of ongoing chronic condition care to monitor lung function over time and guide management decisions.
When Should You Speak With a GP About Breathing Symptoms?
Consider booking a GP appointment for:
- Persistent or recurring cough.
- Recurrent or unexplained wheezing
- Breathlessness that is worsening or affecting daily life
- Reduced exercise tolerance without a clear cause
- Breathing symptoms related to previous smoking or occupational exposure
- Changes in asthma or COPD symptoms that are harder to manage than usual
If you or someone else is having severe difficulty breathing, call Triple Zero (000) for an ambulance rather than waiting for a routine GP or spirometry appointment.
FAQs
Does a spirometry test hurt?
Spirometry is generally not painful, although the repeated forceful breathing can feel tiring and may briefly cause coughing or light-headedness.
Can spirometry diagnose asthma?
Spirometry can provide objective evidence of variable airflow limitation and bronchodilator responsiveness, which can support an asthma assessment when the clinical history is consistent. Normal spirometry does not exclude asthma, particularly when symptoms are not present during the test.
Can spirometry show COPD?
Spirometry is an important test when COPD is suspected. A pattern of persistent airflow limitation on post-bronchodilator spirometry is part of the assessment. Still, results must be interpreted with symptoms, exposure history and clinical examination rather than from numbers alone.
Can I use my inhaler before a spirometry test?
Follow the instructions given by your clinic. Whether to withhold an inhaler before testing depends on the medicine and the reason for the test. Do not stop any prescribed medicine without being specifically advised to do so.
Can spirometry be normal if you have asthma?
Yes. Spirometry results can be within the normal range if symptoms are absent at the time of testing. A normal result does not always rule out asthma, and further assessment or repeat testing may sometimes be needed. If your child is being assessed for asthma, the childhood asthma article on this site also covers when lung-function testing may be considered.
Discussing Lung Function With Your GP
Spirometry is one tool that may help a GP assess respiratory symptoms. The results do not replace a full clinical assessment, and a normal result does not always mean every concern has been resolved.
If you have been advised to have lung-function testing or would like persistent breathing symptoms assessed, book a GP appointment with Clarence Town Healthcare to discuss the next appropriate step.