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Influence of Population Variation of Physiological Parameters in Computational Models of Space PhysiologyThe earliest manifestations of Visual Impairment and Intracranial Pressure (VIIP) syndrome become evident after months of spaceflight and include a variety of ophthalmic changes, including posterior globe flattening and distension of the optic nerve sheath. Prevailing evidence links the occurrence of VIIP to the cephalic fluid shift induced by microgravity and the subsequent pressure changes around the optic nerve and eye. Deducing the etiology of VIIP is challenging due to the wide range of physiological parameters that may be influenced by spaceflight and are required to address a realistic spectrum of physiological responses. Here, we report on the application of an efficient approach to interrogating physiological parameter space through computational modeling. Specifically, we assess the influence of uncertainty in input parameters for two models of VIIP syndrome: a lumped-parameter model (LPM) of the cardiovascular and central nervous systems, and a finite-element model (FEM) of the posterior eye, optic nerve head (ONH) and optic nerve sheath. Methods: To investigate the parameter space in each model, we employed Latin hypercube sampling partial rank correlation coefficient (LHSPRCC) strategies. LHS techniques outperform Monte Carlo approaches by enforcing efficient sampling across the entire range of all parameters. The PRCC method estimates the sensitivity of model outputs to these parameters while adjusting for the linear effects of all other inputs. The LPM analysis addressed uncertainties in 42 physiological parameters, such as initial compartmental volume and nominal compartment percentage of total cardiac output in the supine state, while the FEM evaluated the effects on biomechanical strain from uncertainties in 23 material and pressure parameters for the ocular anatomy. Results and Conclusion: The LPM analysis identified several key factors including high sensitivity to the initial fluid distribution. The FEM study found that intraocular pressure and intracranial pressure had dominant impact on the peak strains in the ONH and retro-laminar optic nerve, respectively; optic nerve and lamina cribrosa stiffness were also important. This investigation illustrates the ability of LHSPRCC to identify the most influential physiological parameters, which must therefore be well-characterized to produce the most accurate numerical results.
Document ID
20170004120
Acquisition Source
Glenn Research Center
Document Type
Presentation
Authors
Myers, J. G.
(NASA Glenn Research Center Cleveland, OH United States)
Feola, A.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Werner, C.
(Zin Technologies, Inc. Cleveland, OH, United States)
Nelson, E. S.
(NASA Glenn Research Center Cleveland, OH 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
May 1, 2017
Publication Date
October 26, 2016
Subject Category
Aerospace Medicine
Report/Patent Number
GRC-E-DAA-TN36570
Meeting Information
Meeting: Annual Meeting of the American Society for Gravitational and Space Research
Location: Cleveland, OH
Country: United States
Start Date: October 26, 2016
End Date: October 29, 2016
Sponsors: American Society for Gravitational and Space Biology
Funding Number(s)
WBS: WBS 516724.01.02.10
CONTRACT_GRANT: NNC14CA02C
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
biomechanics
physiological response
gravitational physiology
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