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Effects of short-term exposure to head-down tilt on cerebral hemodynamics: a prospective evaluation of a spaceflight analog using phase-contrast MRI
Umeå University, Faculty of Medicine, Department of Radiation Sciences.
Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Biomedical Laboratory Science.
Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
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2016 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 12, 1466-1473 p.Article in journal (Refereed) PublishedText
Abstract [en]

Alterations in cerebral hemodynamics in microgravity are hypothesized to occur during spaceflight and could be linked to the Visual Impairment and Intracranial Pressure syndrome. Head-down tilt (HDT) is frequently used as a ground-based analog to simulate cephalad fluid shifts in microgravity; however, its effects on cerebral hemodynamics have not been well studied with MRI techniques. Here, we evaluate the effects of 1) various HDT angles on cerebral arterial and venous hemodynamics; and 2) exposure to 1% CO2 during an intermediate HDT angle (-12 degrees) as an additional space-related environmental factor. Blood flow, cross-sectional area (CSA), and blood flow velocity were measured with phase-contrast MRI in the internal jugular veins, as well as the vertebral and internal carotid arteries. Nine healthy male subjects were measured at baseline (supine, 0 degrees) and after 4.5 h of HDT at -6 degrees, -12 degrees (with and without 1% CO2), and -18 degrees. We found a decrease in total arterial blood flow from baseline during all angles of HDT. On the venous side, CSA increased with HDT, and outflow decreased during -12 degrees HDT (P = 0.039). Moreover, the addition of 1% CO2 to -12 degrees HDT caused an increase in total arterial blood flow (P = 0.016) and jugular venous outflow (P = 0.001) compared with -12 degrees HDT with ambient atmosphere. Overall, the results indicate decreased cerebral blood flow during HDT, which may have implications for microgravity-induced cerebral hemodynamic changes.

Place, publisher, year, edition, pages
2016. Vol. 120, no 12, 1466-1473 p.
Keyword [en]
visual impairment and intracranial pressure, microgravity, cerebral blood flow, head-down tilt, MRI
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URN: urn:nbn:se:umu:diva-124145DOI: 10.1152/japplphysiol.00841.2015ISI: 000378054800011PubMedID: 27013606OAI: diva2:951091
Available from: 2016-08-05 Created: 2016-07-21 Last updated: 2016-08-05Bibliographically approved

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Ambarki, KhalidEklund, AndersMalm, Jan
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Department of Radiation SciencesBiomedical Laboratory ScienceDepartment of Pharmacology and Clinical Neuroscience
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