Spirometry (spy-ROM-uh-tree) is a common test used to check how well your lungs work. It measures how much air you breathe in, how much you breathe out and how quickly you breathe out.

Healthcare professionals use spirometry to diagnose asthma, chronic obstructive pulmonary disease (COPD) and other conditions that affect the ability to breathe. Healthcare professionals also may use spirometry from time to time to check the condition of your lungs and see whether a treatment for a lifelong lung condition is helping you breathe better.

If your healthcare professional thinks your symptoms may be caused by a lung condition such as asthma, COPD, chronic bronchitis, emphysema or pulmonary fibrosis, you may be asked to get a spirometry test. If you've already been diagnosed with a lung condition, your healthcare professional may use spirometry from time to time to check how well your medicines are working and whether your breathing problems are under control.

Your healthcare professional can order spirometry before a planned surgery to check if you have enough lung function for surgery. Also, spirometry may be used to screen for lung disorders related to your job.

Spirometry is generally a safe test. You may feel short of breath or dizzy for a moment after you do the test.

Because the test requires some physical effort, it isn't done if you've recently had a heart attack or another heart condition. Rarely, the test causes severe breathing problems.

Follow your healthcare professional's instructions about whether you should avoid using medicines that you breathe in or any other medicines before the test. Also:

• Wear loose clothing, so it's not hard to take a deep breath.
• Don't eat a large meal before your test, so it will be easier to breathe.

The main spirometry measurements include:

• Forced vital capacity (FVC). This is the largest amount of air that you can forcefully breathe out after breathing in as deeply as you can. An FVC reading that's lower than what's typical indicates restricted breathing.
• Forced expiratory volume (FEV). This is how much air you can force out of your lungs in one second. This reading helps your healthcare professional figure out how serious your breathing problem is. Lower FEV-1 readings mean greater blockages in the bronchial tubes.