• Spirometry: airflow and obstruction
• Lung volumes: restriction and hyperinflation
• Gas transfer (DLCO): alveolar–capillary function
• Bronchodilator response: reversibility of obstruction

Tests may involve:

• Normal breathing
• Forced inhalation/exhalation
• Breath-holding
• Inhaled medication challenges

Duration: 20–45 minutes, depending on tests involved

• Not all tests are needed for everyone: The type and number of lung function tests depend on your symptoms and clinical question.
• Your effort matters: Some parts of the test require you to breathe in or out in a specific way. Clear instructions and repeat attempts help make the results accurate.
• If you feel unwell: Let your clinician know if you have a chest infection or feel unwell on the day, as this can affect results and the test may be rearranged.
• Medication use: You may be asked to avoid certain inhalers before testing. You will be given clear instructions if this applies to you.
• During the test: You can stop at any time if you feel uncomfortable, dizzy, or breathless. Staff will monitor you throughout.
• Understanding your results: Lung function tests are interpreted together with your symptoms, medical history, and other investigations.
• Hygiene and safety: Single-use mouthpieces and filters are used to reduce the risk of infection.