To study the effect of relocation from 3200m (Aksay) to 760m (Bishkek) in highlanders with High Altitude Pulmonary Hypertension (HAPH) who permanently live >2500m on sleep disordered breathing

This research in highlanders with HAPH diagnosed by echocardiography and defined by a RV/RA >30 mmHg who permanently live at HA >2500 m will have nocturnal respiratory sleep studies near their living altitude in Aksay at 3200 m and on night 1 and 6 at 760m after relocation.

Inclusion Criteria:

• Permanently living >2500 m
• HAPH diagnosed with a minimum RV/RA of 30 mmHg assessed by echocardiography at an altitude of 3200 m
• Written informed consent

Exclusion Criteria:

• Highlanders who cannot follow the study investigations,
• Patients with moderate to severe concomitant lung disease (FEV1<70% or forced vital capacity <70%), severe parenchymal lung disease, heavy smoking >20 cigarettes/day or >20 pack-years.
• Coexistent unstable systemic hypertension or coronary artery disease that required adjustment of medication within the last 2 months
• Regular use of medication that affects control of breathing (benzodiazepines, opioids, acetazolamide)