Lead Sponsor

University of Zurich

Age

18 - No limit years

Sex

ALL

Healthy Volunteers

No

•Informed consent as documented by signature (Appendix Informed Consent Form)
•PH class I (PAH) or IV (CTEPH) diagnosed according to guidelines: mean pulmonary artery pressure \>20 mmHg, pulmonary vascular resistance ≥3 wood units, pulmonary arterial wedge pressure ≤15 mmHg during baseline measures at the diagnostic right-heart catheterization

•resting partial pressure of oxygen \<8 kilopascal at Zürich altitude on ambient air
•exposure to an altitude \>1000 m for ≥3 nights during the last 2 weeks before the study
•inability to follow the procedures of the study
•patients who take nitrates
•other clinically significant concomitant end-stage disease (e.g., renal failure, hepatic dysfunction)