Who Should Get Long-Term Oxygen Therapy and When?
Although oxygen supplementation relieves hypoxemia, it may increase oxidative stress, an insult thought to be involved in the pathogenesis of COPD (59). Hence, the value of oxygen treatment in COPD should be determined by clinical trials of sufficient duration to detect effects on mortality. Although there is clear value for long-term oxygen in those with resting PaO2 <= 55 mm Hg (3), there have not been adequate trials to assess the benefit of this treatment in other groups (67). Studies are needed in those with moderate hypoxemia, those with nocturnal oxyhemoglobin desaturation, and those who desaturate with ambulation. Possible effects of oxygen therapy on cognitive function and quality of life need to be assessed. 9. How Can Exercise Capacity Be Increased? Exercise limitation is prevalent in COPD and is predictive of mortality among those with severe disease (68, 69). The physiologic basis of this limitation is multifactorial (70). Ventilatory impairment, sensation of dyspnea, card
