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Heart failure impairs cerebral oxygenation during exercise in patients with COPD

To the Editor: 

Impaired systemic oxygen delivery, particularly during exertion, is the key pathophysiological feature shared by chronic obstructive pulmonary disease (COPD) and heart failure with reduced left ventricular ejection fraction (HFrEF). Unfortunately, COPD and HFrEF frequently coexist not only because of their high individual prevalence but also due to common risk factors, including cigarette smoking, advanced age, oxidative stress and systemic inflammation [1].

It is expected that any reduction in the rate of oxygen transfer due to COPD and/or HFrEF would be particularly deleterious to tissues heavily dependent upon constant oxygen flow, such as the central nervous system (as reviewed in [2]). Exercise cerebral oxygenation (Cox) (as noninvasively determined by near-infrared spectroscopy) depends upon the dynamic balance between the instantaneous rate of oxygen delivery and oxygen utilisation [3]. Koike et al . [4], for instance, reported that congestive heart failure (CHF) HFrEF was associated with appreciable decreases in COx during exertion. Our laboratory found that exercise COx might be impaired in some patients with more advanced COPD, even if not overtly hypoxaemic [5]. Moreover, improvement in cardiac output with noninvasive ventilation (under the same arterial oxygen content) had positive effects on COx in COPD [6]. These data suggest that reduced cerebral blood flow might be mechanistically linked to impaired exercise COx in some patients with moderate-to-severe COPD. It is conceivable that the presence of HFrEF would further deteriorate this scenario by adding components of dysfunctional cerebral autoregulation, lower cardiac output and hypocapnia-induced vasoconstriction [4]. The compound effects of HFrEF plus COPD on …