Breathing trainer is an active breathing exercise device. It follows the basic principles of resistance training and increases inspiratory muscle strength and endurance through the resistance set by the resistance training device. Exhaling slowly and forcefully helps with gas exchange and the removal of carbon dioxide from the lungs.

     Compared with isolated lip breathing and abdominal breathing, the use of breathing trainers for respiratory rehabilitation training has a more significant effect on the lung function, blood oxygen saturation, and exercise ability of patients with COPD. Among them, the three-ball trainer produces different inhalation or exhalation impedances by adjusting the diameter of the airflow port.