Have you wondered how your doctor decides if you have asthma? Diagnosing asthma involves a combination of a physical exam, personal and medical history, and lung function tests to confirm your diagnosis and set up the right treatment plan.

Asthma is a chronic disease that causes you to have inflammation in your airways. Doctors use lung function tests to see how your lungs function or to see if you have inflammation.

Spirometry is one of the most common lung function tests. You will blow into a mouthpiece that is hooked up to a device, called a spirometer, or a computer. This tells your doctor:

• How much air you can inhale
• How much air you can exhale
• How fast you can exhale
  
  

The results of this test will determine what happens next. If the results show you have reduced lung function, you will be asked to inhale a medicine. This medicine is called a bronchodilator (brahn-ko-DIE-ah-lay-tor). It opens up your airways if they are inflamed.

Your doctor will give the medicine time to work. Then they will have you take the spirometry test again. If your results have improved, your doctor may diagnose you with asthma.

At follow-up visits, you may take a spirometry test so your doctor can monitor your lung function and make sure your treatment plan is working.