title: Evidence for hysteresis in the cerebral pressure-flow relationship in healthy men.
abstract: The cerebrovasculature is more efficient at compensating for pharmacologically induced transient hypertension versus transient hypotension. Whether this phenomenon exists during nonpharmacologically induced hypertension and hypotension is currently unknown. We compared the percent change in mean velocity in the middle cerebral artery (MCAvmean) per percent change in mean arterial pressure (MAP) (%ΔMCAVmean/%ΔMAP) during transient hypertension and hypotension induced during squat-stand maneuvers performed at 0.05 Hz (20-s cycles) and 0.10 Hz (10-s cycles) in 58 male volunteers. %ΔMCAvmean/%ΔMAP was attenuated by 25% (P= 0.03, 0.05 Hz) and 47% (P< 0.0001, 0.10 Hz) during transient hypertension versus hypotension. Thus, these findings indicate that the brain in healthy men is better adapted to compensate for physiologically relevant transient hypertension than hypotension.NEW & NOTEWORTHYThe novel finding of this study is that the change in middle cerebral artery mean flow velocity is attenuated during hypertension compared with hypotension physiologically induced by oscillations in blood pressure in men. These results support that the human brain is more effective at compensating for transient hypertension than hypotension.
authors.affiliation: Department of Kinesiology, Faculty of Medicine, Université Laval, Québec City, Québec, Canada; patrice.brassard@kin.ulaval.ca.|Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec City, Québec, Canada; and.
authors.forename: Patrice
authors.initials: P
authors.lastname: Brassard
authors.affiliation: Department of Kinesiology, Faculty of Medicine, Université Laval, Québec City, Québec, Canada.|Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec City, Québec, Canada; and.
authors.forename: Hélène
authors.initials: H
authors.lastname: Ferland-Dutil
authors.affiliation: Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Smirl
authors.affiliation: Department of Kinesiology, Faculty of Medicine, Université Laval, Québec City, Québec, Canada.|Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec City, Québec, Canada; and.
authors.forename: Myriam
authors.initials: M
authors.lastname: Paquette
authors.affiliation: Department of Kinesiology, Faculty of Medicine, Université Laval, Québec City, Québec, Canada.|Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec City, Québec, Canada; and.
authors.forename: Olivier
authors.initials: O
authors.lastname: Le Blanc
authors.affiliation: Department of Kinesiology, Faculty of Medicine, Université Laval, Québec City, Québec, Canada.|Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec City, Québec, Canada; and.
authors.forename: Simon
authors.initials: S
authors.lastname: Malenfant
authors.affiliation: Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
mesh_terms: D000328:Adult; D000368:Aged; D062186:Arterial Pressure; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D007022:Hypotension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000502:physiology; D012016:Reference Values; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
keywords: cerebrovascular blood flow; exercise; hypertension; hypotension; hysteresis