Nocturnal cerebral oxygenation in patients with pulmonary hypertension staying at 2500m. RCT.

<bold>Introduction:</bold> High-altitude (HA) travel marks a growing trend. This elevates concerns about the impact of hypoxic environments on individuals' health, particularly the brain, among vulnerable patient groups like those with pulmonary hypertension (PH) due to pulmonary vascular diseases (PVD). Therefore, this study examined the cerebral homeostasis in PVD patients staying overnight at HA, and aimed to elucidate potential therapeutic benefits of nocturnal oxygen therapy (NOT). <bold>Material and Methods:</bold> In this randomized controlled cross-over trial, stable patients with PVD namely pulmonary arterial hypertension (PAH) or distal chronic thromboembolic PH (CTEPH) underwent overnight near-infrared spectroscopy (derived parameter: cerebral tissue oxygenation [CTO] and cerebral oxygen desaturation index [cODI] defined as a decrease in CTO of ≥4%) at 470m and during the first night at 2500m. NOT was provided to patients if nocturnal SpO2 dropped <80% for >30min. <bold>Results:</bold> Overall, 16 PVD patients (7 women; 13 PAH, 3 distal CTEPH) aged 56±14years were included. At 470m, the nocturnal CTO was 66.3±1.6% but remained unchanged at 2500m with 66.3±1.5%; mean difference of −0.2% (−3.9 to 3.5). At HA, cODI increased by 1.8events/hour (0.3 to 3.7, P<0.05), versus 470m. NOT, applied to 44% of PVD patients due to severe hypoxemia significantly improved nocturnal CTO and cODI beyond values at 470m. <bold>Conclusion:</bold> At 2500m, 44% of stable PVD patients required NOT due to severe hypoxemia. In those with nocturnal SpO2 >80%, overall CTO remained unchanged despite nocturnal hypoxemia. These findings suggest sufficient nocturnal cerebral protection at 2500m in PVD. The study underscores the beneficial role of NOT.