Nocturnal Cerebral Oxygenation in Low-Altitude Residents With Pulmonary Vascular Disease Staying Overnight at High...

Whether hypoxia during popular high-altitude travel negatively affects cerebral oxygenation in vulnerable patients with pulmonary vascular disease (PVD) is unknown. We studied overnight cerebral tissue oxygen saturation (CTO) and desaturation index (cODI) in PVD-patients at 2500 m and effects of supplemental oxygen therapy (SOT). In this randomized-controlled crossover trial, stable PVD-patients diagnosed with pulmonary arterial or distal chronic thromboembolic pulmonary hypertension (PAH/CTEPH) had CTO and cODI (decrease in CTO ≥ 4%) assessed overnight at 470 m and 2500 m along with fingertip pulseoximetry (SpO₂) and desaturation index (aODI). For safety, SOT was given if SpO₂ dropped < 80% for > 30 min and stratified analysis accordingly. Primary endpoint was the difference in CTO between 470 and 2500 m. 16 PVD-patients (7 women; 13 PAH, 3 CTEPH), (mean ± SD) 56 ± 14 years old, were included per-protocol. At 470 m, the mean nocturnal CTO was 66.3 ± 1.6% and SpO₂ 90.3 ± 0.8%. At 2500 m on ambient air, CTO was unchanged 65.9 ± 1.6% (mean difference -0.4%; 95% CI -4.0 to 3.2) despite a lower SpO₂ of 83.6 ± 0.8; -6.7 (-8.7 to -4.6%). At 2500 vs. 470 m, cODI increased by 3.1 events/hour (-0.3 to 6.6). SOT needed by 50% of PH-patients improved SpO₂ by +7.5 (4.9 to 10.0), but not CTO and cODI (+3.6% (-1.0 to 8.2)) and -3.8 events/hour (-8.1 to 0.5). In PVD-patients on ambient air at 2500 m, nocturnal CTO remained unchanged compared to 470 m despite lower SpO₂. SOT promptly improved SpO₂ without affecting cerebral oxygenation. These findings suggest sufficient nocturnal cerebral protection at 2500 m in PVD.