Critical closing pressure is the primary modulator of cerebrovascular resistance in older adults

Abstract

RationaleCerebrovascular resistance (CVR), calculated from mean cerebral blood flow (CBF) and mean arterial blood pressure (ABP), can be further characterized by two independent parameters: critical closing pressure (CrCP) and resistance area product (RAP). These parameters are believed to reflect differences in the metabolic and myogenic control of CVR, respectively. The objective of this study was to assess how CVR, CrCP and RAP interrelate in a healthy aging population and how they adapt to postural change.MethodsSixty‐three older adults (36 women, 74 ± 5 years) were categorized in tertiles according to CVR determined from bilateral internal carotid artery blood flow and mean ABP. Apparent CrCP and RAP were estimated from continuous middle cerebral artery blood flow velocity and ABP in supine, sitting and standing postures.ResultsIndividuals in the highest tertile for CVR had both higher ABP (P < 0.001) and lower CBF (P < 0.001) than the lowest tertile. Lying supine, CVR was directly related to CrCP (r = 0.43, P < 0.001), but not RAP (P = 0.697). CrCP was reduced (P < 0.001) and RAP was slightly increased (P = 0.010) in upright posture.ConclusionHigh CVR in aging was primarily related to CrCP which might reflect structural changes leading to lower CBF in these individuals. Reduced CrCP with upright posture protects the brain from hypoperfusion during sitting and standing. Funded by CIHR, HSF, NSERC