Spirometer Say: spih-rah-muh-tur A spirometer is an instrument that measures how well your lungs are working. To use one, a person breathes into a mouthpiece. The doctor may ask the person to breathe normally or to take a deep breath and blow the air quickly out of the lungs, like blowing up a balloon. A recording device measures the amount of air inhaled or exhaled and how much time each breath took. These measurements can help the doctor find out if a person has a lung problem, such as 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.