A spirometer measures how well your lungs work to help doctors diagnose asthma and other breathing problems. This test is as easy as blowing out your birthday candles. 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.