Funding Status:
Terminated - A formerly active task that was stopped before its completion date due to deselection, descoping, reorganization etc.
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Procurement Mechanism(s):
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Aims:
Specific Aim 1: To determine the impact of sequential +1 Gz followed by -0.3 Gz stress
on cerebrovascular and ocular structure and function without the orthostatic intolerance
countermeasures normally applied in astronauts returning from space flight.
Hypothesis: Following +1.0 Gz exposure, –Gz exposure will increase jugular vein
distention and pressure, increase intraocular and intracranial pressure, and distend
optic nerve sheath diameter but not change cerebral blood flow velocity.
Specific Aim 2: To determine the effect of anti-orthostatic countermeasures (fluid
loading, gradient compression garments, legs up posture with foot pressure) on the +1
Gz to -0.3 Gz induced fluids shift and subsequent impact on cerebral and ocular
structure and function.
Hypothesis: The addition of the anti-orthostatic countermeasures will exacerbate ocular
and vascular effects induced by the HDT fluid shift and will overcome the ability of
cerebral autoregulation to minimize these changes resulting in clinically significant
elevations in ICP.