Friend or foe: Face masks in patients with COPD at high altitude.

High-altitude environments impose unique physiological challenges due to reduced barometric pressure and lower inspired oxygen partial pressure, raising concerns about the safety of face mask use in individuals with chronic obstructive pulmonary disease. While evidence at sea level shows that surgical and N95 masks modestly impair gas exchange-slightly reducing oxygen uptake, oxygen saturation-they consistently increase perceived exertion, dyspnea, and fatigue. Limited studies conducted under hypobaric conditions-typically involving small sample sizes, brief mask-wearing periods, and healthy participants. However, data at higher altitudes and in patients with COPD remain scarce. Emerging epidemiological evidence suggests that COPD prevalence may decrease with increasing altitude, yet high-altitude residence can alter pathophysiology and could increase vulnerability to hypoxemia and hypercapnia during mask use in advanced disease. Existing studies in COPD at sea level report generally modest physiological effects with short-term mask use, but their small sample sizes and short exposure durations limit generalizability. This perspective highlights the urgent need for well-designed studies evaluating both acute and chronic physiological responses to prolonged mask use in COPD patients at high altitudes to inform evidence-based public health recommendations.