Exercise Performance on Ambient Air vs. Low-Flow Oxygen Therapy in Pulmonary Vascular Disease (PVD)

Inclusion Criteria: * Minimum 18 years of age * Written informed consent * Patients with diagnosed pulmonary arterial hypertension (PAH), distal chronic thromboembolic pulmonary hypertension (CTEPH) * Former desaturation under exercise defined as Spo2-decrease \>3% * Treated with a stable drug therapy (with no changes for at least 14 days prior to screening) Exclusion Criteria: * Severe hypoxemia needing supplemental oxygen therapy defined as partial pressure of O2 (PaO2) \< 6.9 Kilopascal (kPa) * Pregnancy * Unability or contraindications to undergo the investigated intervention * Unability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc