Spirometry is the most common of the lung function tests. These tests look at how well your lungs work. Spirometry shows how well you breathe in and out. Breathing in and out can be affected by lung diseases such as chronic obstructive pulmonary disease (COPD), asthma, pulmonary fibrosis and cystic fibrosis.

Reversibility testing is done in some cases where the diagnosis of the lung condition is not clear. For this test, you will be asked to do spirometry as described above. You will then be given a medicine by inhaler or nebuliser which may open up the airways. A nebuliser allows a medicine to be inhaled like a fine mist, through a mask. The spirometry test is then repeated 30 minutes or so afterwards. The aim of this is to see if your airways open wider with medication or not. Generally, asthma has more of a reversible element to the airways obstruction, compared with COPD.