Nocturnal Heart Rate and Cardiac Repolarization in Lowlanders With Chronic Obstructive Pulmonary Disease at High Altitude: Data From a Randomized, Placebo-Controlled Trial of Nocturnal Oxygen Therapy

Background: Chronic obstructive pulmonary disease (COPD) is associated with cardiovascular disease. We investigated whether sleeping at altitude increases nocturnal heart rate (HR) and other markers of risk or arrhythmias in lowlanders COPD this can be prevented by oxygen therapy (NOT). Methods: Twenty-four patients, median age 66 years forced expiratory volume 1 s (FEV ) 55% predicted, living <800 m underwent sleep studies Zurich (490 m) during 2 sojourns days each St. Moritz (2,048 separated 2-week washout m. During nights 2,048 m, patients received either NOT NOT) ambient air placebo) 3 L/min via nasal cannula according to a randomized, placebo-controlled crossover trial. Sleep comprised ECG pulse oximetry measure HR, rhythm, HR-adjusted QT interval (QTc), mean saturation (SpO ). Results: In the first 490 placebo, NOT, medians (quartiles) SpO were 92% (90; 94), 86% (83; 89), 97% (95; 98) HR 73 (66; 82), 82 (71; 85), 78 bpm (67; 74) ( P < 0.05 all respective comparisons). QTc increased from 417 ms (404; 439) 426 (405; 440) placebo 0.05) was 420 = NS vs. placebo). The number extrabeats complex similar over conditions. Conclusions: While staying experienced hypoxemia association an prolongation interval. significantly improved lowered without changing QTc. Whether would reduce arrhythmia longer remains elucidated.