Observing Physiological Changes in Patients With Long-term Oxygen Therapy

Inclusion Criteria: * Age ≥ 18-year-old, and * Chronic respiratory disease including a) chronic obstructive pulmonary disease, b) interstitial lung disease, c) pulmonary hypertension, d) bronchiectasis, and * Prescribed new LTOT due to a chronic respiratory disease with resting and/or exertional hypoxemia, and * Able to speak/read/understand German or French, and * Willing and able to understand and provide signed informed consent Exclusion Criteria: * Pregnant or lactating women, or * Inability to follow the procedures/instructions of the study (e.g. due to language, psychological disorders, dementia, etc.), or * Patients having a subordination link to the investigators, or * Patients with isolated nocturnal oxygen therapy or LTOT prescription for a heart disease, sleep associated breathing disorder, neuromuscular disease or lung cancer, or * Known participation in another human research project (ClinO/HRO) that may affect the objectives of this study.