Referring to findings from their own work [1], the authors pointed out that nocturnal hypoxemia may be an important determinant of systemic inflammation and, thus, cardiovascular morbidity and mortality in COPD. We have similarly observed elevated circulating levels of interleu-kin-6 and plasma fibrinogen in patients with stable COPD compared with age-, gender, and body-mass-index matched controls [2,3]. In fact, systemic inflammatory markers were amongst the most significant predictors of systemic vascular dysfunction and, thus, cardiovascular morbidity and mortality in patients with COPD [3]. However, we did not detect an independent relationship between arterial oxygenation and systemic inflammation in these reports, though we did not assess nocturnal hypoxemia explicitly. Furthermore, we were not able to find a link between the use of long-term oxygen therapy and cardiovascular function in COPD (3), suggesting that chronic hypoxemia may have less direct cardiovascular consequences than systemic inflammation.
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