title: Oscillatory lower body negative pressure impairs task related functional hyperemia in healthy volunteers.
abstract: Neurovascular coupling refers to the link between an increase in neural activity in response to a task and an increase in cerebral blood flow denoted "functional hyperemia." Recent work on postural tachycardia syndrome indicated that increased oscillatory cerebral blood flow velocity (CBFv) was associated with reduced functional hyperemia. We hypothesized that a reduction in functional hyperemia could be causally produced in healthy volunteers by using oscillations in lower body negative pressure (OLBNP) to force oscillations in CBFv. CBFv was measured by transcranial Doppler ultrasound of the left middle cerebral artery. We used passive arm flexion applied during eight periodic 60-s flexion/60-s relaxation epochs to produce 120-s periodic changes in functional hyperemia (at 0.0083 Hz). We used -30 mmHg of OLBNP at 0.03, 0.05, and 0.10 Hz, the range for cerebral autoregulation, and measured spectral power of CBFv at all frequencies. Arm flexion power performed without OLBNP was compared with arm flexion power during OLBNP. OLBNP power performed in isolation was compared with power during OLBNP plus arm flexion. Cerebral flow velocity oscillations at 0.05 Hz reduced and at 0.10 Hz eliminated functional hyperemia, while 0.03 Hz did not reach significance. In contrast, arm flexion reduced OLBNP-induced oscillatory power at all frequencies. The interactions between OLBNP-driven CBFv oscillations and arm flexion-driven CBFv oscillations are reciprocal. Thus induced cerebral blood flow oscillations suppress functional hyperemia, and functional hyperemia suppresses cerebral blood flow oscillations. We conclude that oscillatory cerebral blood flow produces a causal reduction of functional hyperemia.
authors.affiliation: Department of Pediatrics, New York Medical College, Valhalla, New York; and Department of Physiology, New York Medical College, Valhalla, New York; julian_stewart@nymc.edu.
authors.forename: Julian M
authors.initials: JM
authors.lastname: Stewart
authors.affiliation: Department of Pediatrics, New York Medical College, Valhalla, New York; and.
authors.forename: Keshawadhana
authors.initials: K
authors.lastname: Balakrishnan
authors.affiliation: Department of Epidemiology and Biostatistics, Baystate Medical Center, Tufts University School of Medicine, Springfield, Massachusetts; and.
authors.forename: Paul
authors.initials: P
authors.lastname: Visintainer
authors.affiliation: School of Physical Education Sport & Exercise Science, Ball State University, Muncie, Indiana.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Del Pozzi
authors.affiliation: Department of Pediatrics, New York Medical College, Valhalla, New York; and.
authors.forename: Zachary R
authors.initials: ZR
authors.lastname: Messer
authors.affiliation: Department of Pediatrics, New York Medical College, Valhalla, New York; and.
authors.forename: Courtney
authors.initials: C
authors.lastname: Terilli
authors.affiliation: Department of Pediatrics, New York Medical College, Valhalla, New York; and Department of Physiology, New York Medical College, Valhalla, New York;
authors.forename: Marvin S
authors.initials: MS
authors.lastname: Medow
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D006940:Hyperemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008150:Lower Body Negative Pressure / Q000379:methods*; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D054972:Postural Orthostatic Tachycardia Syndrome / Q000503:physiopathology; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
keywords: functional hyperemia; lower body negative pressure; neurovascular coupling