Synopsis
Obtain and interpret quality-assured airflow measurements, distinguish obstruction from possible restriction, and use variability or reversibility as evidence without confusing a test result with a diagnosis.
- Check identity, age, sex, height, indication, contraindications, current symptoms and recent bronchodilator use before testing.
- FEV1 is the volume expired in the first second; FVC is the total forced expiratory volume; the FEV1/FVC ratio identifies airflow obstruction.
- Interpret against appropriate reference values and the lower limit of normal where available; a fixed ratio below 0.70 supports COPD only in the right clinical context and can overdiagnose older adults.
Key red flags
Acute cardiorespiratory instability, active significant haemoptysis, recent relevant thoracic/abdominal/eye surgery, untreated pneumothorax, severe infection-control risk or inability to follow instructions requires deferral or specialist assessment.
Investigation priorities
Decide whether testing is safe and whether bronchodilator washout is appropriate.
Management branches
Any acceptable spirometry result.
- 1. Confirm acceptability, repeatability, reference equation and whether result is pre- or post-bronchodilator.
- 2. Read FEV1/FVC first: below LLN indicates obstruction; then use FEV1 to describe impairment without equating it to symptom burden.
Key medicines
Salbutamol for bronchodilator reversibility testing400 micrograms inhaled through a spacer (typically 4 actuations of a 100 microgram metered-dose inhaler), then repeat spirometry after the protocol interval, commonly about 15 minutes.
Ipratropium as an alternative reversibility agent in specialist protocolsA common protocol uses 160 micrograms inhaled (for example 8 actuations of a 20 microgram inhaler) with repeat testing after about 30 minutes; follow the physiology laboratory protocol and product licence.