Lung Function Tests The term "lung function" refers to how well a person is breathing. There are several tests that help doctors find out how good a person's lung function is and determine whether the person has asthma. One of these tests, called a spirometry test, involves taking a breath and then blowing the air out as fast and as long as possible. Lung function tests can help a doctor find out if someone has asthma. Back to Articles Related Articles Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.