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Fluid ShiftsNASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 30% of ISS astronauts experience more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the space flight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration space flight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during space flight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's pre-flight condition and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid pulsatility); (5) ocular measures (optical coherence tomography, intraocular pressure, 2-dimensional ultrasound including optic nerve sheath diameter, globe flattening, and retina-choroid thickness, Doppler ultrasound of ophthalmic and retinal arteries, and veins); (6) cardiac variables by ultrasound (inferior vena cava, tricuspid flow and tissue Doppler, pulmonic valve, stroke volume, right heart dimensions and function, four-chamber views); and (7) ICP measures (tympanic membrane displacement, distortion-product otoacoustic emissions, and ICP calculated by MRI). On the ground, acute head-down tilt will induce cephalad fluid shifts, whereas LBNP will oppose these shifts. Controlled Mueller maneuvers will manipulate cardiovascular variables. Through interventions applied before, during, and after flight, we intend to fully evaluate the relationship between fluid shifts and the VIIP syndrome. This study has been selected for flight implementation and is one of the candidate investigations being considered for the one year mission.
Document ID
20140003756
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Stenger, Michael
(Wyle Integrated Science and Engineering Group Houston, TX, United States)
Hargens, A.
(California Univ. San Diego, CA, United States)
Dulchavsky, S.
(Henry Ford Hospital Detroit, MI, United States)
Ebert, D.
(Wyle Integrated Science and Engineering Group Houston, TX, United States)
Lee, S.
(Wyle Integrated Science and Engineering Group Houston, TX, United States)
Sargsyan, A.
(Wyle Integrated Science and Engineering Group Houston, TX, United States)
Martin, D.
(Wyle Integrated Science and Engineering Group Houston, TX, United States)
Lui, J.
(California Univ. San Diego, CA, United States)
Macias, B.
(California Univ. San Diego, CA, United States)
Arbeille, P.
(California Univ. San Diego, CA, United States)
Platts, S.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
April 25, 2014
Publication Date
February 12, 2014
Subject Category
Aerospace Medicine
Life Sciences (General)
Report/Patent Number
JSC-CN-30010
Meeting Information
Meeting: NASA Human Research Program Investigators'' Meeting
Location: Galveston, TX
Country: United States
Start Date: February 12, 2014
End Date: February 13, 2014
Sponsors: National Space Biomedical Research Inst., Universities Space Research Association
Distribution Limits
Public
Copyright
Public Use Permitted.
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