Clinical Research Directory

Inclusion Criteria: * Adult patients aged 18-80 years and of all genders * Permanent residence \> 2600 m * Diagnosis of pulmonary arterial hypertension PAH (PAHHA-Group) according to guidelines * Patients are stable on therapy * NYHA (new york heart association) functional class I-III. * written informed consent to participate in the study. Exclusion Criteria: * Age \<18 years or \>80 years * unstable condition * Patients who cannot follow the study investigations * Patient permanently living \< 2600m. * Patients who traveled and stayed overnight at altitudes \<2000 m in the past 4 weeks. * Patients with moderate to severe concomitant lung disease (FEV1\<70% or forced vital capacity \<70%), severe parenchymal lung disease, severe smokers (\>20 cigarettes/day) * Severely hypoxemic patients at Quito permanently having persistent SpO2 (oxygen saturation by pulseoximetry) \<80% on ambient air. * Patient with a non-corrected ventricular septum defect * Relevant concomitant other disease of the heart, kidney, liver, blood (anemia hemoglobin\<11 g/dl)