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  • 1
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    Energy balance and the composition of weight loss during prolonged space flight (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Integrated metabolic balance analysis, Skylab integrated metabolic balance analysis and computer simulation of fluid-electrolyte responses to zero-g, overall mission weight and tissue losses, energy balance, diet and exercise, continuous changes, electrolyte losses, caloric and exercise requirements, and body composition are discussed.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-171745 , NAS 1.26:171745 , TIR-2114-MED-2012
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  • 2
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    Water immersion and its computer simulation as analogs of weightlessness (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experimental studies and computer simulations of water immersion are summarized and discussed with regard to their utility as analogs of weightlessness. Emphasis is placed on describing and interpreting the renal, endocrine, fluid, and circulatory changes that take place during immersion. A mathematical model, based on concepts of fluid volume regulation, is shown to be well suited to simulate the dynamic responses to water immersion. Further, it is shown that such a model provides a means to study specific mechanisms and pathways involved in the immersion response. A number of hypotheses are evaluated with the model related to the effects of dehydration, venous pressure disturbances, the control of ADH, and changes in plasma-interstitial volume. By inference, it is suggested that most of the model's responses to water immersion are plausible predictions of the acute changes expected, but not yet measured, during space flight. One important prediction of the model is that previous attempts to measure a diuresis during space flight failed because astronauts may have been dehydrated and urine samples were pooled over 24-hour periods.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-171746 , NAS 1.26:171746 , TIR-2114-MED-2005
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  • 3
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    Computer simulation analysis of the behavior of renal-regulating hormones during hypogravic stress (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A computer simulation of a mathematical circulation model is used to study the alterations of body fluids and their electrolyte composition that occur in weightlessness. The behavior of the renal-regulating hormones which control these alterations is compared in simulations of several one-g analogs of weightlessness and space flight. It is shown that the renal-regulating hormones represent a tightly coupled system that responds acutely to volume disturbances and chronically to electrolyte disturbances. During hypogravic conditions these responses lead to an initial suppression of hormone levels and a long-term effect which varies depending on metabolic factors that can alter the plasma electrolytes. In addition, it is found that if pressure effects normalize rapidly, a transition phase may exist which leads to a dynamic multiphasic endocrine response.
    Keywords: AEROSPACE MEDICINE
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  • 4
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    An integrative approach to space-flight physiology using systems analysis and mathematical simulation (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An approach was developed to aid in the integration of many of the biomedical findings of space flight, using systems analysis. The mathematical tools used in accomplishing this task include an automated data base, a biostatistical and data analysis system, and a wide variety of mathematical simulation models of physiological systems. A keystone of this effort was the evaluation of physiological hypotheses using the simulation models and the prediction of the consequences of these hypotheses on many physiological quantities, some of which were not amenable to direct measurement. This approach led to improvements in the model, refinements of the hypotheses, a tentative integrated hypothesis for adaptation to weightlessness, and specific recommendations for new flight experiments.
    Keywords: AEROSPACE MEDICINE
    Type: The 11th Space Simulation Conf.; p 149-162
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  • 5
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    Computer simulations of postural change, water immersion and bedrest - An integrative approach for understanding the spaceflight response (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Mathematical modeling techniques were used to simulate the fluid electrolyte (F-E) responses during gravity unloading. It is shown that the response to weightlessness can best be understood by separately examining the acute (hours to days) and chronic (days to weeks) phases, and assuming the presence of normal, although complex, feedback regulatory processes. Headward shifts of fluid are shown to be primarily responsible for acute body losses of extracellular F-E. Losses of body water are closely related to the volume of fluid shifts from the legs. A diuresis is predicted within the first several hours of hypogravity, and this may be obscured by a reduced F-E intake; on Skylab, early F-E losses occurred primarily by deficit intake.
    Keywords: AEROSPACE MEDICINE
    Type: p. S-31
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  • 6
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    Mathematical modeling of fluid-electrolyte alterations during weightlessness (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Fluid electrolyte metabolism and renal endocrine control as it pertains to adaptation to weightlessness were studied. The mathematical models that have been particularly useful are discussed. However, the focus of the report is on the physiological meaning of the computer studies. A discussion of the major ground based analogs of weightlessness are included; for example, head down tilt, water immersion, and bed rest, and a comparison of findings. Several important zero g phenomena are described, including acute fluid volume regulation, blood volume regulation, circulatory changes, longer term fluid electrolyte adaptations, hormonal regulation, and body composition changes. Hypotheses are offered to explain the major findings in each area and these are integrated into a larger hypothesis of space flight adaptation. A conceptual foundation for fluid electrolyte metabolism, blood volume regulation, and cardiovascular regulation is reported.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-171881 , NAS 1.26:171881 , TIR-2114-MED-4001
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  • 7
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    Analysis of head-down tilt as an analog of weightlessness using a methematical simulation model (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Antiorthostasis or head down tilt of a moderate degree was used as a ground based analog of weightless space flight to study headward fluid shifts, decreased plasma volume, orthostatic intolerance and muscular skeletal degradation. A mathematical model was used to help interpret these observations. The model proved most valuable for these studies was originally developed as a description of the major circulatory, fluid and electrolyte control systems. Two different experimental studies are employed to validate the model. The first is a 24 hour head down tilt study and the second is a 7 day head down bed rest study. The major issues addressed include the reduction in plasma volume, the dynamic changes of venous pressure and cardiac output, the extent of central hypervolemia during long term zero g exposure, the existence of an early diuresis, the mechanisms which alter the renal regulating hormones during the short term and long term periods, the significance of potassium loss on other zero g responses, and the role of transcapillary filtration in adjusting fluid shifts. The use of mathematical models as an interpretive and analysis technique for experimental research for space life science is illustrated.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-171870 , NAS 1.26:171870 , TIR-2114-MED-4003
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  • 8
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    Causes and consequences of reduced blood volume in space flight - A multi-discipline modeling study (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A group of mathematical models of various physiological systems have been developed and applied to studying problems associated with adaptation to weightlessness. One biomedical issue which could be addressed by at least three of these models from varying perspectives was the reduction in blood volume that universally occurs in astronauts. Accordingly, models of fluid-electrolyte, erythropoiesis, and cardiovascular regulation were employed to study the causes and consequences of blood volume loss during space flight. This analysis confirms the notion that alterations of blood volume are central to an understanding of adaptation to prolonged space flight. More importantly, the modeling studies resulted in specific hypotheses accounting for plasma volume and red cell mass losses and testable predictions concerning the behavior of the circulatory system.
    Keywords: AEROSPACE MEDICINE
    Type: Summer Computer Simulation Conference; Jul 11, 1983 - Jul 13, 1983; Vancouver; Canada
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  • 9
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    Simulation of cardiovascular response to acceleration stress following weightless exposure (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Physiological adjustments taking place during space flight tend to reduce the tolerance of the crew to headward (+Gz) acceleration experienced during the reentry phase of the flight. This reduced tolerance to acceleration stress apparently arises from an adaptation to the microgravity environment of space, including a decrease in the total circulating blood volume. Countermeasures such as anti-g garments have long been known to improve the tolerance to headward g-force, but their effectiveness in space flight has not been fully evaluated. The simulation study presented in this paper is concerned with the response of the cardiovascular system to g-stress following cardiovascular deconditioning, resulting from exposure to weightlessness, or any of its ground-based experimental analogs. The results serve to demonstrate the utility of mathematical modeling and computer simulation for studying the causes of orthostatic intolerance and the remedial measures to lessen it.
    Keywords: AEROSPACE MEDICINE
    Type: Summer Computer Simulation Conference; Jul 11, 1983 - Jul 13, 1983; Vancouver; Canada
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  • 10
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    Space Station and the life sciences (1983)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Previous fundamental research in space life sciences is examined, and consideration is devoted to studies relevant to Space Station activities. Microgravity causes weight loss, hemoconcentration, and orthostatic intolerance when astronauts returns to earth. Losses in bone density, bone calcium, and muscle nitrogen have also been observed, together with cardiovascular deconditioning, fluid-electrolyte metabolism alteration, and space sickness. Experiments have been performed with plants, bacteria, fungi, protozoa, tissue cultures, invertebrate species, and with nonhuman vertebrates, showing little effect on simple cell functions. The Spacelab first flight will feature seven life science experiments and the second flight, two. Further studies will be performed on later flights. Continued life science studies to optimize human performance in space are necessary for the efficient operation of a Space Station and the assembly of large space structures, particularly in interaction with automated machinery.
    Keywords: AEROSPACE MEDICINE
    Type: AIAA PAPER 83-7089
    Format: text
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