Lung exerciser 3 Ball Spirometer Breathing can be hard after you had a surgery. You may find that you can only take small, shallow breaths. Breathing this way makes it harder to get air into your lungs and can cause fluid and mucus to build up in your lungs. Using our incentive 3-ball spirometer 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 and faster recovery of your diseases.