Using an incentive spirometer or commonly known as a lung exerciser can help you practice taking deep breaths, which can help open your airways, prevent fluid or mucus from building up in your lungs, and make it easier for you to breathe.
An incentive spirometer/lung exerciser is a handheld device that exercises your lungs and measures how much air you can breathe in. It tells you and your doctor how well your lungs are working.
A flexible plastic tube is connected to a large and small air column. The large column has a piston or ball that moves up each time you breathe in. This column measures how much air you breathe in. Your effort is marked in units of milliliters. A smaller column measures your effort as "good," "better," or "best."
Read more about it on Angooor Blog.