Dyspnea, cough, and chronic mucus hypersecretion are common symptoms in patients with Chronic Obstructive Pulmonary Disease (COPD), which increases risk of infections followed by exacerbations, often leading to hospitalization, disease progression and mortality. This patient group requires lifelong treatment in healthcare. A mobile application was developed to facilitate adherence to evidence-based guidelines for tailored breathing and airway clearance techniques to enhance self-management. The app is only in Norwegian and has a Norwegian name which is "Pust Deg Bedre" (PDB). The PDB app is fully developed and tested and can be downloaded for free. The app seems promising as a treatment tool, but has not yet been clinical evaluated. This project aims to 1) explore the feasibility of providing the app for patients with COPD, 2) explore the patients' with COPD experiences with the use of the PDB-app in treating dyspnea and mucus secretion, 3) explore the physiotherapists' experiences with the use of the PDB-app in treating dyspnea and mucus secretion, 4) explore the physiotherapists' experiences with implementing the PDB-app in treatment of patients with COPD, 5) explore the patients' experiences with the education in use of the PDB-app, and 6) At a 6-month follow up: explore the physiotherapists experiences with the usefulness and applicability of PBD-app, and to generally explore their experiences with participating in the project.