HA Residents With PVD, 6MWD Assessed at HA (2840m) vs LA (Sea Level)

Inclusion Criteria: * Adult patients 18-80 years old of both genders, * Residence \> 2500m of altitude * diagnosed with precapillary PH (mean pulmonary artery pressure (mPAP) \>20 mmHg, pulmonary artery wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) ≥2 WU (wood units) by right heart catheterization) with PH being classified as PAH or CTEPH according to guidelines * Patients stable on therapy * NYHA (new york heart association) functional class I-III * Provided 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 \< 2500m. * Patients with moderate to severe concomitant lung disease (FEV1\<70% or forced vital capacity \<70%), severe parenchymal lung disease, severe smokers (\>20 igarettes/day) * Severely hypoxemic patients at Quito permanently have persistent SpO2 (oxygen saturation by pulseoximetry) \<80% on ambient air. * Patients with chronic mountain sickness (Hemoglobin \> 19 g/dl in women, \>21 g/dl in men) * Patient with a non-corrected ventricular septum defect * Relevant concomitant other disease of the heart, kidney, liver, blood (anemia hemoglobin\<11 g/dl)