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Microgravity-Induced Physiological Fluid Redistribution: Computational Analysis to Assess Influence of Physiological ParametersSpace flight impacts human physiology in many ways, the most immediate being the marked cephalad (headward) shift of fluid upon introduction into the microgravity environment. This physiological response to microgravity points to the redistribution of blood and interstitial fluid as a major factor in the loss of venous tone and reduction in heart muscle efficiency which impact astronaut performance. In addition, researchers have hypothesized that a reduction in astronaut visual acuity, part of the Visual Impairment and Intracranial Pressure (VIIP) syndrome, is associated with this redistribution of fluid. VIIP arises within several months of beginning space flight and includes a variety of ophthalmic changes including posterior globe flattening, distension of the optic nerve sheath, and kinking of the optic nerve. We utilize a suite of lumped parameter models to simulate microgravity-induced fluid redistribution in the cardiovascular, central nervous and ocular systems to provide initial and boundary data to a 3D finite element simulation of ocular biomechanics in VIIP. Specifically, the lumped parameter cardiovascular model acts as the primary means of establishing how microgravity, and the associated lack of hydrostatic gradient, impacts fluid redistribution. The cardiovascular model consists of 16 compartments, including three cerebrospinal fluid (CSF) compartments, three cranial blood compartments, and 10 thoracic and lower limb blood compartments. To assess the models capability to address variations in physiological parameters, we completed a formal uncertainty and sensitivity analysis that evaluated the relative importance of 42 input parameters required in the model on relative compartment flows and compartment pressures. Utilizing the model in a pulsatile flow configuration, the sensitivity analysis identified the ten parameters that most influenced each compartment pressure. Generally, each compartment responded appropriately to parameter variations associated with itself and adjacent compartments. However, several unexpected interactions between components, such as between the choroid plexus and the lower capillaries, were found, and are due to simplifications in the formulation of the model. The analysis illustrates that highly influential parameters and those that have unique influences within the model formulation must be tightly controlled for successful model application.
Document ID
Acquisition Source
Glenn Research Center
Document Type
Myers, J. G.
(NASA Glenn Research Center Cleveland, OH United States)
Eke, Chika
(National Space Biomedical Research Inst. (NSBRI) Houston, TX, United States)
Werner, C.
(ZIN Technologies, Inc. Middleburg Heights, OH, United States)
Nelson, E. S.
(NASA Glenn Research Center Cleveland, OH United States)
Mulugeta, L.
(Universities Space Research Association Houston, TX, United States)
Feola, A.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Raykin, J.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Samuels, B.
(Alabama Univ. Birmingham, AL, United States)
Ethier, C. R.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Date Acquired
October 19, 2016
Publication Date
February 8, 2016
Subject Category
Aerospace Medicine
Report/Patent Number
Meeting Information
Meeting: 2016 NASA Human Research Program Investigators'' Workshop (HRP IWS 2016)
Location: Galveston, TX
Country: United States
Start Date: February 8, 2016
End Date: February 11, 2016
Sponsors: NASA Johnson Space Center, National Space Biomedical Research Inst. (NSBRI)
Funding Number(s)
WBS: WBS 516724.01.02.10
Distribution Limits
Public Use Permitted.
gravitational physiology
physiological response
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