Spirometry

Category: Lung & Breathing Tests · All lung & breathing tests

What it is

Spirometry measures how much air you can breathe out and how fast, by blowing into a mouthpiece connected to a measuring device. Key numbers are FVC (total blown out) and FEV1 (blown out in the first second), whose pattern distinguishes obstructive diseases (asthma, COPD) from restrictive ones.

Why it is done

It is the core test for diagnosing and monitoring asthma and COPD, investigating breathlessness and chronic cough, and assessing lungs before surgery.

How to prepare

You may be asked to avoid inhalers for a set time before the test and avoid smoking, heavy meals, caffeine and vigorous exercise beforehand — your appointment letter specifies. Wear loose clothing. Tell the team about recent chest infection, surgery, or heart problems.

What happens during the procedure

Sitting upright with a nose clip on, you breathe in fully and blast out into the mouthpiece as hard and long as possible, then in again quickly for some measurements. At least three good efforts are taken. You may then be given a bronchodilator inhaler and repeat the test to see if airways open up (reversibility). It takes about 20 to 30 minutes.

Afterwards — recovery & results

You can go straight back to normal activities. Blowing hard can make you feel briefly light-headed or cough. Results are compared with predicted values for your age, sex, height and ethnicity and are usually explained at your clinic appointment.

Risks & considerations

There are minimal risks; the test is effort-dependent, so submaximal blowing can mislead — the technician will coach you to get reliable results. It is avoided or postponed after recent eye, chest or abdominal surgery or heart attack, per your team's advice.

Frequently asked questions

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