Introduction: Stable patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension (PH) wish to undergo altitude sojourns or air travel but fear disease worsening. This pilot study investigates health effects of altitude sojourns and potential benefits of nocturnal oxygen therapy (NOT) in PH patients. Methods: Nine stable PH patients, age 65 (47; 71) years, 5 women, in NYHA class II, on optimized medication, were investigated at 490 m and during two sojourns of 2 days/nights at 2,048 m, once using NOT, once placebo (ambient air), 3 L/min per nasal cannula, according to a randomized crossover design with 2 weeks washout at <800 m. Assessments included safety, nocturnal pulse oximetry (SpO₂), 6-min walk distance (6 MWD), and echocardiography. Results: At 2,048 m, two of nine patients required medical intervention, one for exercise-induced syncope, one for excessive nocturnal hypoxemia (SpO₂ < 75% for >30 min). Both recovered immediately with oxygen therapy. Two patients suffered from acute mountain sickness. In 6 patients with complete data, nocturnal mean SpO₂ and cyclic SpO₂ dips reflecting sleep apnea significantly differed from 490 to 2,048 m with placebo, and 2,048 m with NOT (medians, quartiles): SpO₂ 93 (91; 95)%, 89 (85; 90)%, 97 (95; 97)%; SpO₂ dips 10.4/h (3.1; 26.9), 34.0/h (5.3; 81.3), 0.3/h (0.1; 2.3). 6 MWD at 490, 2,048 m without and with NOT was 620 m (563; 720), 583 m (467; 696), and 561 m (501; 688). Echocardiographic indices of heart function and PH were unchanged at 2,048 m with/without NOT vs. 490 m. Conclusions: 7/9 PH patients stayed safely at 2,048 m but revealed hypoxemia, sleep apnea, and reduced 6 MWD. Hemodynamic changes were trivial. NOT improved oxygenation and sleep apnea. The current pilot trial is important for designing further studies on altitude tolerance of PH patients.

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