Spirometry

Spirometry is a breathing test that measures how much air your lungs can hold and how fast you can blow it out.

During the test, you breathe into a mouthpiece connected to a device called a spirometer. The spirometer records two key values: the total volume of air you can force out after a deep breath, and the amount you can push out in the first second of that effort. These numbers tell the doctor whether your airways — the tubes that carry air into your lungs — are open and working normally, narrowed, or blocked.

Spirometry is used both to diagnose lung conditions and to monitor how well a known condition is being controlled. Doctors also use it as a routine check for people who are at risk of lung disease before any symptoms appear.

• Asthma (a condition where airways narrow and swell, causing wheezing and breathlessness)
• COPD — chronic obstructive pulmonary disease (long-term damage to the lungs, often caused by smoking)
• Chronic bronchitis (long-lasting inflammation of the airways)
• Emphysema (damage to the tiny air sacs in the lungs)
• Pulmonary fibrosis (scarring of lung tissue)
• Monitoring lung function before major surgery
• Assessing lung health in people who smoke or who work around dust, fumes, or chemicals
• Checking how well an inhaler or other lung treatment is working
• Unexplained persistent cough or shortness of breath

There are some situations where spirometry is usually postponed or performed with extra care. Your doctor will decide whether the test is safe for you at a given time.

• Recent heart attack or unstable angina (chest pain from a struggling heart)
• Recent eye surgery, as forceful breathing can briefly raise pressure inside the eye
• Recent abdominal or chest surgery where straining could affect the healing wound
• Severe, uncontrolled high blood pressure at the time of testing
• A current significant respiratory infection such as active tuberculosis

Spirometry is a non-invasive (no needles, no cuts, no radiation) breathing test that is very well tolerated by most people; serious complications are rare.

• Lightheadedness or dizziness from breathing hard — this passes within a minute or two of resting
• Brief shortness of breath or chest tightness, especially in people who already have a lung condition
• Coughing during or just after the effort
• A small, temporary rise in blood pressure from the forced breathing effort
• In people with certain eye or abdominal conditions, a brief rise in internal pressure — this is why the test may be postponed after surgery in those areas
• Very rarely, a pneumothorax (collapsed lung) can be triggered in someone who already has very fragile lung tissue — your doctor will screen for this risk beforehand

Preparing well helps ensure the results are accurate and reflect your true lung function, rather than being affected by food, medication, or substances you have recently taken.

In the hours before the test, most clinics ask patients to avoid eating a large meal, avoid smoking, and avoid vigorous exercise. Alcohol is also usually avoided on the day of the test. Wear loose, comfortable clothing that does not restrict your chest or stomach.

Some inhaled medications — such as bronchodilators (medicines that open up the airways) — may be paused before the test if the doctor wants to see your baseline lung function without them. Other medications are usually continued as normal. Always follow the specific instructions given by the clinic, as practices vary.

No blood tests or imaging scans are routinely needed before spirometry. The technician may take your height and weight before starting, because normal lung values differ based on your size, age, and sex.

During the test itself, the steps typically go like this:

• You sit upright in a chair. Your height and weight are recorded if not already done.
• A soft clip is placed on your nose to make sure all air passes through the mouthpiece.
• You seal your lips tightly around the mouthpiece.
• The technician coaches you to breathe in as deeply as you possibly can.
• You then blast the air out as hard and as fast as you can, keeping going until your lungs feel completely empty — this usually takes at least six seconds.
• You may be asked to breathe in forcefully again at the end of the effort.
• The manoeuvre is repeated, usually at least three times, so the technician can confirm consistent results.
• In some cases, a bronchodilator (airway-opening medicine) is given after the first set of measurements, and the breathing efforts are repeated after a short wait to see whether the medication improves the results. This is called a bronchodilator reversibility test.

Spirometry requires no recovery period in the way a surgical procedure does. Most people feel completely normal within a few minutes of finishing the test and can go home or return to work straight away. If you felt dizzy or short of breath during the test, the technician will ask you to sit and rest until you feel steady.

• No wound care is needed — there is no incision or injection site.
• If your regular inhaled medication was paused for the test, your doctor will advise when to resume it.
• Avoid very strenuous exercise for the rest of the day if you felt any chest tightness or dizziness during the test.
• Your results are usually reviewed by a respiratory medicine specialist (a doctor who focuses on lung conditions), who will interpret the numbers in the context of your age, height, sex, and symptoms.
• Your doctor will explain the results at a follow-up appointment and discuss whether further tests — such as a CT scan of the chest or an allergy test — are needed.
• If spirometry is being used to monitor a known condition like asthma or COPD, repeat tests are usually scheduled at regular intervals to track changes over time.
• Contact the clinic if you develop unusual chest pain, worsening breathlessness, or feel unwell in the hours after the test, although this is uncommon.