Spirometry

In order to diagnose and monitor asthma, your health care provider examines you. He or she listens to your chest and asks you to breathe. You are asked questions about your symptoms, triggers and any family history of asthma or allergies. Tests may also be done.

Spirometry is an easy test that tells your health care provider how well your lungs are working. The spirometer measures the amount of air you exhale (breathe out) and how quickly you can exhale completely.

What does the spirometer measure?

It can take several different measures of your breath:

• Forced vital capacity (FVC) – This is the total amount of air you exhale in a single, long breath.
• Forced expiratory volume in one second (FEV1) – This is the amount of air you exhale in the first second.
• FEV1/FVC – This is the amount of air exhaled in the first second compared to the total amount of air exhaled. It's given as a fraction or a percentage. In general, the higher the FEV1/FVC, the better. Normal values depend on your age.
• Peak expiratory flow (PEF) – This is a measure of how fast you can exhale. It can be tested with a spirometer or a peak flow meter.