Postural Effects on Cerebral Blood Flow and Autoregulation
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Introduction: Cerebral autoregulation (CA) is thought to maintain constant cerebral blood flow (CBF), yet CBF decreases when moving from a supine to a seated posture. We sought to determine why CBF decreases when one sits up and if this reflects imperfect CA. Methods: Bilateral cerebral blood flow velocity (CBFv) in the middle cerebral arteries, mean arterial blood pressure (MABP) at the level of the heart, cardiac output (Q), and end-tidal carbon dioxide (PETCO2) were measured in 18 (11 female and 7 male) healthy 26±9 year-olds during periods of supine and seated rest. Participants lay supine, ...