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Effect 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. Local vascular reflexes in lower leg. On ground.

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slide1

Effect 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.

slide3

On ground

Vasoconstriction:

Blood flow

Gravity

Flow detector

slide4

In space

No gravitational stress

No vasoconstriction

slide5

After flight

Vasoconstriction ?

Gravity

Flow detector

slide6

Background

  • Astronauts might faint after spaceflight (orthostatic intolerance)
  • Several mechanisms might account for this:
  • - Low blood volume.
  • - Weak pressure reflexes.
  • - Attenuated muscle strength.
  • - Increased distensibility of veins (compliance).
  • - Weak local vascular reflexes?
slide7

Hypothesis

The local vascular reflexes in the lower leg are attenuated after spaceflight.

slide8

Purpose of experiment

  • 1. To measure:
    • arm blood pressure and
    • blood flow under the skin (subcutaneous tissue) in the lower leg before and after spaceflight.

2. Local vascular resistance is calculated by blood pressure/flow.

possible risks or discomforts
Possible Risks or Discomforts
  • Subcutaneous injection: Minimal risk
  • - Some pain and discomfort during needle insertion.
  • - Possibility of infection. Aseptic technique and sterile disposable equipment will minimize this possibility.
possible risks or discomforts10
Possible Risks or Discomforts
  • Radioactive Isotope Injection (133Xe; inert gas in sterile isotonic saline solution): Minimal Risk
  • - 80 µCi in 0.2 ml saline.
  • - No evidence of effects on normal physiology.
slide11

Experimental Flow

  • Preflight
  • L-TBD: Flexible
  • Supine:
  • - Leg horizontal 7 min
  • - Lower leg down 7 min
  • Leg horizontal 7 min
  • Blood pressure
  • Blood flow in the leg
  • Postflight
  • R+0
  • Supine:
  • - Leg horizontal 7 min
  • - Lower leg down 7 min
  • Leg horizontal 7 min
  • Blood pressure
  • Blood flow in the leg
sessions pre postflight
Sessions – Pre/Postflight

Injection of tracer

slide14

Crew Requirements

For Each Study Day (L-X (TBD) and R+0):

  • No physical exercise on study day
  • before experiment.
  • Notes on orthostatic feelings (postflight).
  • Crew time: 1 hr.
slide15

Experimental Success

  • Accurate blood flow detection in
  • totally resting leg.
  • Postflight measurements as early
  • as possible.
slide16

Experimental Benefits

  • Understanding mechanisms of postflight fainting.
  • Understanding local vascular reflexes (basic physiology).
  • Correlations to disease (e.g. heart failure).