A lung function test for asthma

The test involves doing a baseline spirometry — a simple test that measures how much air you can exhale after taking a very deep breath. You'll do this by breathing into a mouthpiece attached to a specialised device. Next, you'll breathe in several doses of a powder through an inhaler. The powder is a sugar-based substance that causes a mild reaction if you have sensitive airways. After each dose, your respiratory physiologist will repeat the spirometry to assess for any changes. The whole test takes around an hour.

Your consultant will explain the test to you and answer any questions you may have. They'll let you know if there is anything specific you need to do to prepare. This may include avoiding certain medications, caffeine, smoking or vigorous exercise before your test.