Effect of Nocturnal Oxygen Therapy on Nocturnal Hypoxemia and Sleep Apnea Among Patients With Chronic Obstructive Pulmonary Disease Traveling to 2048 Meters

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Abstract
Chronic obstructive pulmonary disease (COPD) is characterized by chronic airflow limitation related to airway inflammation associated with airway narrowing and destruction of the lung parenchyma. Given that COPD is highly prevalent and the fourth leading cause of death, it is a major health problem worldwide.1 Although COPD is a progressive condition, medical treatment may improve symptoms in many patients. Today, millions of tourists travel to high altitude for leisure or work activities, and many patients with COPD are among them. Studies have found that acute ascent to altitude above 2500 m causes hypoxemia, periodic breathing, disturbed sleep, and exercise intolerance in healthy travelers,2,3 whereas short-term altitude exposures between 2000 m and 2500 m (equivalent to pressurized airplane cabins during long-distance flights) seem to be unproblematic for healthy individuals. However, patients with preexisting lung diseases, such as COPD, may experience severe hypoxemia at high altitude because of disease-related ventilatory limitations and impaired gas exchange.4-8 Thus, in a randomized clinical trial among patients with moderate to severe COPD (ie, forced expiratory volume in the first second of expiration [FEV1] between 30% and 80% predicted) who were exposed for 2 days at 2590 m,4 we observed an incidence of 24% of altitude-related adverse health effects (ARAHEs) requiring medical intervention. Moreover, endurance of submaximal exercise at this altitude was reduced by more than half compared with near sea level,5 and the patients with COPD experienced nocturnal hypoxemia, frequent sleep apnea,7 and autonomic dysregulation.8 In a randomized, placebo-controlled trial among 118 lowlanders with COPD,6 preventive dexamethasone treatment improved nocturnal hypoxemia and sleep apnea during a stay at 3100 m; however, dexamethasone did not reduce the incidence of ARAHEs and induced hyperglycemia. Supplemental oxygen therapy may improve oxygenation and exercise capacity in patients with COPD who are acutely exposed to high altitude.9,10 While daytime oxygen administration during mountain outdoor activities is inconvenient or may be unpractical, nocturnal oxygen therapy (NOT) could be a feasible way to prevent severe hypoxemia, breathing disturbances, and ARAHEs in patients with COPD during altitude sojourns. Therefore, the purpose of this randomized, placebo-controlled trial was to evaluate the hypothesis that NOT would improve nocturnal oxygen saturation and breathing instability as well as reduce the incidence of ARAHEs in lowlanders with COPD staying at high altitude.

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