Effect of nocturnal oxygen therapy on exercise performance of COPD patients at 2048 m: data from a randomized clinical trial

Abstract

This trial evaluates whether nocturnal oxygen therapy (NOT) during a stay at 2048 m improves altitude-induced exercise intolerance in lowlanders with chronic obstructive pulmonary disease (COPD). 32 lowlanders with moderate to severe COPD, mean ± SD forced expiratory volume in the first second of expiration (FEV1) 54 ± 13% predicted, stayed for 2 days at 2048 m twice, once with NOT, once with placebo according to a randomized, crossover trial with a 2-week washout period at < 800 m in-between. Semi-supine, constant-load cycle exercise to exhaustion at 60% of maximal work-rate was performed at 490 m and after the first night at 2048 m. Endurance time was the primary outcome. Additional outcomes were cerebral tissue oxygenation (CTO), arterial blood gases and breath-by-breath measurements (http://www.ClinicalTrials.gov NCT02150590). Mean ± SE endurance time at 490 m was 602 ± 65 s, at 2048 m after placebo 345 ± 62 s and at 2048 m after NOT 293 ± 60 s, respectively (P < 0.001 vs. 490 m). Mean difference (95%CI) NOT versus placebo was − 52 s (− 174 to 70), P = 0.401. End-exercise pulse oximetry (SpO2), CTO and minute ventilation ($${\dot{\text{V}}}_{{\text{E}}}$$ V ˙ E ) at 490 m were: SpO2 92 ± 1%, CTO 65 ± 1%, $${\dot{\text{V}}}_{{\text{E}}}$$ V ˙ E 37.7 ± 2.0 L/min; at 2048 m with placebo: SpO2 85 ± 1%, CTO 61 ± 1%, $${\dot{\text{V}}}_{{\text{E}}}$$ V ˙ E 40.6 ± 2.0 L/min and with NOT: SpO2 84 ± 1%; CTO 61 ± 1%; $${\dot{\text{V}}}_{{\text{E}}}$$ V ˙ E 40.6 ± 2.0 L/min (P < 0.05, SpO2, CTO at 2048 m with placebo vs. 490 m; P = NS, NOT vs. placebo). Altitude-related hypoxemia and cerebral hypoxia impaired exercise endurance in patients with moderate to severe COPD and were not prevented by NOT.

Effects of Acute Exposure and Acclimatization to High-Altitude on Oxygen Saturation and Related Cardiorespiratory Fitness in Health and Disease

“…In this study, 32 patients with COPD performed a maximal exercise ramp test on the day of arrival at 2048 m. The mean VO 2 peak declined by 7% at 2048 m compared to 490 m, which was associated with a SpO 2 peak decline of 8%. In the same study and identical to the study at 2590 m, submaximal exercise performance on a semi-supine bicycle was performed after the first night at 2048 m. Similar to 2590 m, endurance time was strongly reduced by 36% compared to 2048 m; SpO 2 peak declined by 7% [37].…”

Exercise Performance of Lowlanders with Chronic Obstructive Pulmonary Disease Acutely Exposed to 2048 m: A Randomized Cross-Over Trial

“…Moreover, a study performed in the same COPD cohort indicated that hypoxemia-related cerebral hypoxia might be an exercise-limiting factor at this altitude. 12 …”