Does hypercapnia-induced impairment of cerebral autoregulation affect neurovascular coupling? A functional TCD study

Authors: Maggio P, Salinet AS, Panerai RB, Robinson TG.

Neurovascular coupling (NVC) and dynamic cerebral autoregulation (dCA) are both impaired in the acute phase of ischaemic stroke, but their reciprocal interactions are difficult to predict. In order to clarify these aspects, the present study explored NVC in a healthy volunteer population during a surrogate state of impaired dCA, induced by hypercapnia. This study aimed to test if hypercapnia leads to a depression of NVC through an impairment of dCA. Continuous recordings of middle cerebral arteries cerebral blood flow velocity (CBFv), blood pressure (BP), heart rate and end-tidal CO2 were performed in 19 right-handed subjects (aged >45 y) before, during and after 60s of a passive paradigm during normocapnia and hypercapnia. The CBFv response was broken down into subcomponents describing the relative contributions of BP (VBP), critical closing pressure (VCrCP), and resistance area product (VRAP). VRAP reflects myogenic activity in response to BP changes, whereas VCrCP is more indicative of metabolic control. The results revealed that hypercapnia significantly affected NVC, with significant reductions in the relative contribution of VCrCP to the paradigm-induced increase in CBFv. The present study showed that impaired dCA leads to a depression of NVC through an impairment of the metabolic component of CBF control.

Full text and source: Journal of applied physiology

J Appl Physiol. 2013 Jun 6. 

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