Lung function tests measure your breathing to help your doctor or health care provider diagnose and monitor asthma. There are different types of lung functions tests. Your doctor may use a combination of tests to help confirm an asthma diagnosis. Lung function tests can also help them tell if your asthma medicines are working.
Lung function tests are often done before and after inhaling a medicine known as a bronchodilator (brahn-ko-DIE-ah-lay-tor), which opens your airways. If your lung function improves a lot after a bronchodilator, you probably have asthma.
Most lung function tests require you to exhale or inhale using a device or a mouthpiece connected to a device. They are simple tests that are often done in the doctor’s office. Your doctor may ask you to stop taking certain medicines before your appointment.
Spirometry. This is the recommended test to confirm asthma. During this test, you breathe into a mouthpiece that’s connected to a device, called a spirometer, or to a laptop. It measures the amount of air you’re able to breathe in and out and its rate of flow. You will take a deep breath and then exhale forcefully.
Peak flow meter. This test uses a peak flow meter. It’s a small, handheld device that you breathe into to measure the rate at which you can force air out of your lungs. During the test, you breathe in as deeply as you can and then blow into the device as hard and fast as possible. If you’re diagnosed with asthma, you can use a peak flow meter at home to help track your condition. But a peak flow meter cannot be used to diagnose asthma.
FeNO test. A FeNO test – also called exhaled nitric oxide testing – measures the amount of inflammation in your lungs. When you have asthma, your airways become inflamed and produce nitric oxide. This test can tell a doctor how much inflammation is in your airways by measuring the amount of nitric oxide.
Provocation tests. If your other results are normal but you’ve been experiencing signs and symptoms of asthma, your doctor may order a test that produces a mild reaction under controlled laboratory conditions. If you don’t have asthma, you won’t react to the low doses those with asthma will react to.
These lung function tests are some of the most common types used. There are also other types of lung function tests your doctor may use to diagnose and manage your asthma, depending on age, symptoms, medical history and more.
If you have symptoms of asthma, see a board-certified allergist or pulmonologist. Based on your symptoms and medical history, they will talk with you if you need any lung function tests.
Medical Review December 2017.