Impact of Microgravity on the Peripheral Subcutaneous Veno-Arteriolar Reflex in Humans

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Impact of Microgravity on the Peripheral Subcutaneous Veno-Arteriolar Reflex in Humans Principal Investigator: Anders Gabrielsen, M.D. Danish Aerospace Medical Center of Research Co-Investigator: Peter Norsk, M.D., D.M.Sc.

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Local vascular reflexes in lower leg

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On ground Vasoconstriction: Blood stream Gravity Flow indicator

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In space No gravitational stretch No vasoconstriction

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After flight Vasoconstriction ? Gravity Flow indicator

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Background Astronauts may black out after spaceflight (orthostatic bigotry) Several components may represent this: -Low blood volume. - Weak weight reflexes. - Attenuated muscle quality. - Increased distensibility of veins (consistence). - Weak neighborhood vascular reflexes?

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Hypothesis The nearby vascular reflexes in the lower leg are lessened after spaceflight.

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Purpose of investigation 1. To measure: arm circulatory strain and blood stream under the skin (subcutaneous tissue) in the lower leg previously, then after the fact spaceflight. 2. Local vascular resistance is ascertained by pulse/stream.

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Possible Risks or Discomforts Subcutaneous infusion: Minimal hazard - Some torment and distress amid needle addition. - Possibility of contamination. Aseptic technique and clean dispensable equipment will minimize this possibility.

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Possible Risks or Discomforts Radioactive Isotope Injection ( 133 Xe; inactive gas in clean isotonic saline arrangement): Minimal Risk - 80 µCi in 0.2 ml saline. - No confirmation of impacts on typical physiology.

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Experimental Flow Preflight L-TBD: Flexible Supine: - Leg level 7 min - Lower leg down 7 min Leg even 7 min Blood weight Blood stream in the leg Postflight R+0 Supine: - Leg flat 7 min - Lower leg down 7 min Leg flat 7 min Blood weight Blood stream in the leg

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Sessions – Pre/Postflight Injection of tracer

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Sessions – Pre/Postflight 7 min 7 min 7 min

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Crew Requirements For Each Study Day (L-X (TBD) and R+0): No physical practice on study day before test. Notes on orthostatic sentiments (postflight). Group time: 1 hr.

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Experimental Success Accurate blood stream discovery in absolutely resting leg. Postflight estimations as ahead of schedule as could reasonably be expected.

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Experimental Benefits Understanding components of postflight swooning. Understanding nearby vascular reflexes (fundamental physiology). Connections to ailment (e.g. heart disappointment).

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