Effect of Nocturnal Oxygen on Blood Pressure Response to Altitude Exposure in COPD – Data from a Randomized Placebo-Controlled Cross-Over Trial

Martina Meszaros,1 Tsogyal D Latshang,1 Sayaka S Aeschbacher,1 Fabienne Huber,1 Deborah Flueck,1 Mona Lichtblau,1 Stefanie Ulrich,1 Elisabeth D Hasler,1 Philipp M Scheiwiller,1 Lukas Reinhard,1 Silvia Ulrich,1,2 Konrad E Bloch,1– 3 Michael Furian,1 Esther I Schwarz1,3 1Department of Pulmonology and Sleep Disorders Centre, University Hospital Zurich, Zurich, Switzerland; 2Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland; 3Centre of Competence Sleep & Health, University of Zurich, Zurich, SwitzerlandCorrespondence: Esther I SchwarzDepartment of Pulmonology and Sleep Disorders Centre, University Hospital Zurich, Zurich, SwitzerlandTel +41 44 255 11 11Fax +41 44 255 44 51Email estherirene.schwarz@usz.chPurpose: Patients with chronic obstructive pulmonary disease (COPD) are particularly vulnerable to hypoxia-induced autonomic dysregulation. Hypoxemia is marked during sleep. In COPD, altitude exposure is associated with an increase in blood pressure (BP) and a decrease in baroreflex-sensitivity (BRS). Whether nocturnal oxygen therapy (NOT) may mitigate these cardiovascular autonomic changes in COPD at altitude is unknown.Materials and Methods: In a randomized placebo-controlled cross-over trial, 32 patients with moderate-to-severe COPD living < 800 m were subsequently allocated to NOT and placebo during acute exposure to altitude. Measurements were done at low altitude at 490 m and during two stays at 2048 m on NOT (3 L/min) and placebo (3 L/min, ambient air) via nasal cannula. Allocation and intervention sequences were randomized. Outcomes of interest were BP, BRS (from beat-to-beat BP measurement), BP variability (BPV), and heart rate.Results: About 23/32 patients finished the trial per protocol (mean (SD) age 66 (5) y, FEV1 62 (14) % predicted) and 9/32 experienced altitude-related illnesses (8 vs 1, p < 0.05 placebo vs NOT). NOT significantly mitigated the altitude-induced increase in systolic BP compared to placebo (Δ median − 5.8 [95% CI − 22.2 to − 1.4] mmHg, p = 0.05) but not diastolic BP (− 3.5 [95% CI − 12.6 to 3.0] mmHg; p = 0.21) or BPV. BRS at altitude was significantly higher in NOT than in placebo (1.7 [95% CI 0.3 to 3.4] ms/mmHg, p = 0.02).Conclusion: NOT may protect from hypoxia-induced autonomic dysregulation upon altitude exposure in COPD and thus protect from a relevant increase in BP and decrease in BRS. NOT may provide cardiovascular benefits in COPD during conditions of increased hypoxemia and may be considered in COPD travelling to altitude.Keywords: COPD, altitude, oxygen, hypoxia, blood pressure, blood pressure variability, baroreflex sensitivity