Spirometry (Lung Function Test)

How much air, how fast

You breathe into a mouthpiece connected to a machine that measures how much air you can blow out and how quickly — the two numbers that define lung function.

Spirometry is used to diagnose and monitor asthma, COPD and chronic cough, to assess breathlessness, and as a routine pre-employment test in industries where lung health matters. Spirometry is a safe test for most people. Tell us before the test if you have had a heart attack or eye, chest or abdominal surgery in the last month, a collapsed lung, an aneurysm, are coughing blood, or have or may have TB or another chest infection — we will reschedule or take special precautions. Blowing hard can briefly make you dizzy.

Preparation: do not smoke for 1 hour, drink alcohol for 8 hours, eat a heavy meal for 2 hours, or exercise hard for 1 hour before the test. If your doctor has asked for a reversibility test, withhold: short-acting inhalers (salbutamol/levosalbutamol) 4–6 hours; short-acting ipratropium 12 hours; long-acting inhalers (salmeterol/formoterol) 24 hours; tiotropium 36–48 hours — only if your doctor agrees. Never stop an inhaler on your own if you are breathless.