Breathing tests - Spirometry

Spirometry is a breathing test to assess lung function.

The person will be asked to take a deep breath in and then breathe out forcefully and fully into a mouthpiece attached to the spirometry machine. This measures the volume of air which can be exhaled out in one second and the full volume of air that can be exhaled in one forced breath.

Different lung diseases can cause different types of breathing problems. Spirometry can detect restrictive or obstructive problems or a mix of both.

A restrictive defect occurs when the lungs can not fully expand therefore have a lower volume of air than expected, but the air moves normally.

An obstructive defect occurs when there is narrowing of the airways and so the air cannot leave the lungs as quickly as expected, but the volume of air is normal.