title: Effect of an acute increase in central blood volume on cerebral hemodynamics.
abstract: Systemic blood distribution is an important factor involved in regulating cerebral blood flow (CBF). However, the effect of an acute change in central blood volume (CBV) on CBF regulation remains unclear. To address our question, we sought to examine the CBF and systemic hemodynamic responses to microgravity during parabolic flight. Twelve healthy subjects were seated upright and exposed to microgravity during parabolic flight. During the brief periods of microgravity, mean arterial pressure was decreased (-26 ± 1%, P < 0.001), despite an increase in cardiac output (+21 ± 6%, P < 0.001). During microgravity, central arterial pulse pressure and estimated carotid sinus pressure increased rapidly. In addition, this increase in central arterial pulse pressure was associated with an arterial baroreflex-mediated decrease in heart rate (r = -0.888, P < 0.0001) and an increase in total vascular conductance (r = 0.711, P < 0.001). The middle cerebral artery mean blood velocity (MCA Vmean) remained unchanged throughout parabolic flight (P = 0.30). During microgravity the contribution of cardiac output to MCA Vmean was gradually reduced (P < 0.05), and its contribution was negatively correlated with an increase in total vascular conductance (r = -0.683, P < 0.0001). These findings suggest that the acute loading of the arterial and cardiopulmonary baroreceptors by increases in CBV during microgravity results in acute and marked systemic vasodilation. Furthermore, we conclude that this marked systemic vasodilation decreases the contribution of cardiac output to CBF. These findings suggest that the arterial and cardiopulmonary baroreflex-mediated peripheral vasodilation along with dynamic cerebral autoregulation counteracts a cerebral overperfusion, which otherwise would occur during acute increases in CBV.
authors: Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan; ogoh@toyo.jp.
authors: Shigehiko
authors: S
authors: Ogoh
authors: Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan;
authors: Ai
authors: A
authors: Hirasawa
authors: Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas;
authors: Peter B
authors: PB
authors: Raven
authors: Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and.
authors: Thomas
authors: T
authors: Rebuffat
authors: Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and.
authors: Pierre
authors: P
authors: Denise
authors: Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and.
authors: Romain
authors: R
authors: Lericollais
authors: Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan.
authors: Jun
authors: J
authors: Sugawara
authors: Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and.
authors: Hervé
authors: H
authors: Normand
mesh_terms: D000328:Adult; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology; D054022:Cerebrum / Q000098:blood supply*; D006801:Humans; D008297:Male; D011311:Pressoreceptors; D014893:Weightlessness; D055815:Young Adult
keywords: arterial pressure; cardiac output; cerebral blood flow; humans; microgravity