Automated system for integration and display of physiological response data

The system analysis approach was applied in a study of physiological systems in both 1-g and weightlessness, for short and long term experiments. A whole body, algorithm developed as the first step in the construction of a total body simulation system is described and an advanced biomedical computer system concept including interactive display/command consoles is discussed. The documentation of the design specifications, design and development studies, and user's instructions (which include program listings) for these delivered end-terms; the reports on the results of many research and feasibility studies; and many subcontract reports are cited in the bibliography

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 162, January 1977

This bibliography lists 189 reports, articles, and other documents introduced into the NASA scientific and technical information system in December 1976

Cardiovascular Adjustments to Gravitational Stress

The effects of gravity on the cardiovascular system must be taken into account whenever a hemodynamic assessment is made. All intravascular pressure have a gravity-dependent hydrostatic component. The interaction between the gravitational field, the position of the body, and the functional characteristics of the blood vessels determines the distribution of intravascular volume. In turn this distribution largely determines cardiac pump function. Multiple control mechanisms are activated to preserve optimal tissue perfusion when the magnitude of the gravitational field or its direction relative to the body changes. Humans are particularly sensitive to such changes because of the combination of their normally erect posture and the large body mass and blood volume below the level of the heart. Current aerospace technology also exposes human subjects to extreme variations in the gravitational forces that range from zero during space travel to as much an nine-times normal during operation of high-performance military aircraft. This chapter therefore emphasizes human physiology

A numerical model to assess deconditioning of the cardiovascular system in long-term exposure to microgravity. Verification and simulation of Mars mission scenarios

Numerical simulations of the cardiovascular system are particularly important in scenarios where it is difficult to experiment different weightlessness exposure conditions. Technological advances in terms of computational power in the last years, and improvement of algorithms have recently made these techniques more reliable. We report in this paper results from extensive simulations undertaken in a computing facility in our University (UPC BarcelonaTech) aimed at evaluate the risks involved in a long-term exposure to reduced gravity loads for a very extensive range of possible mission scenarios. The simulation allows to introduce different levels of exposure to hypo or hypergravity, and analyze the consequences on relevant figures of cardiovascular deconditioning, such as heart rate, mean stroke volume or vascular resistance. Neurological or thermic stress or aerobic exercise can also be applied in order to better emulate a realistic long-term space mission comprising, for example, Extra Vehicular Activities (EVA) or physical exercise as countermeasures. Gender differences have also been studied, with significant different recommendations given as outcomes of the simulation, for both men and female astronauts. Our model is based on the previous works form Melchier et al. or Heldt et al. who described in analytical terms the process of orthostatic intolerance due to gravity alterations being applied on a human subject. We incorporated these Runge-Kutta equations by using Matlab® and Simulink® software. Results from these models were validated in parabolic flight. We later developed this model to take into account all control system parts involved in the human cardiovascular system, and we finally achieved an electrical-like control model in which we could easily measure the output of the system (vascular resistance, blood volume etc.) as a means to assess the level of cardiovascular deconditioning. Step-by-step changes of gravity and thermal stress were later applied, as well as other real-like mission inputs. Different scenarios of Moon and Mars exploration missions are considered, and their associated risks are quantified. The more relevant results are provided, including the finding that the vascular resistance deconditioning appears to be alike in both microgravity and the reduced gravity at the level of the Moon; which raises concerns for a successful manned Mars mission scenario. This work may contribute to a better understanding of the underlying processes involved for both women in man adaptation to long-term microgravity, and shows the potential of such numerical simulations for designing manned mission scenarios.Peer ReviewedPostprint (published version

Physiological responses to prolonged bed rest in humans: A compendium of research, 1981-1988

Clinical observations and results form more basic studies that help to elucidate the physiological mechanisms of the adaptation of humans to prolonged bed rest. If the authors' abstract or summary was appropriate, it was included. In some cases a more detailed synopsis was provided under the subheadings of purpose, methods, results, and conclusions

Early afterdepolarisations and ventricular arrhythmias in cardiac tissue: a computational study

Afterdepolarisations are associated with arrhythmias in the heart, but are difficult to study experimentally. In this study we used a simplified computational model of 1D and 2D cardiac ventricular tissue, where we could control the size of the region generating afterdepolarisations, as well as the properties of the afterdepolarisation waveform. Provided the size of the afterdepolarisation region was greater than around 1 mm, propagating extrasystoles were produced in both 1D and 2D. The number of extrasystoles produced depended on the amplitude, period, and duration of the oscillatory EAD waveform. In 2D, re-entry was also initiated for specific combinations of EAD amplitude, period, and duration, with the afterdepolarisation region acting as a common pathway. The main finding from this modelling study is therefore that afterdepolarisations can act as potent sources of propagating extrasystoles, as well as a source of re-entrant activation

A Systems Approach to the Physiology of Weightlessness

A systems approach to the unraveling of the complex response pattern of the human subjected to weightlessness is presented. The major goal of this research is to obtain an understanding of the role that each of the major components of the human system plays following the transition to and from space. The cornerstone of this approach is the utilization of a variety of mathematical models in order to pose and test alternative hypotheses concerned with the adaptation process. An integrated hypothesis for the human physiological response to weightlessness is developed

USSR Space Life Sciences Digest, issue 30

This is the thirtieth issue of NASA's Space Life Sciences Digest. It contains abstracts of 47 journal papers or book chapters published in Russian and of three Soviet monographs. Selected abstracts are illustrated with figures and tables from the original. The abstracts in this issue have been identified as relevant to 20 areas of space biology and medicine. These areas include: adaptation, biospheric research, cardiovascular and respiratory systems, endocrinology, equipment and instrumentation, gastrointestinal system, group dynamics, habitability and environmental effects, hematology, human performance, immunology, life support systems, mathematical modeling, metabolism, musculoskeletal system, neurophysiology, nutrition, psychology, radiobiology, and space biology and medicine

Physiologic responses to water immersion in man: A compendium of research

A total of 221 reports published through December 1973 in the area of physiologic responses to water immersion in man were summarized. The author's abstract or summary was used whenever possible. Otherwise, a detailed annotation was provided under the subheadings: (1) purpose, (2) procedures and methods, (3) results, and (4) conclusions. The annotations are in alphabetical order by first author; author and subject indexes are included. Additional references are provided in the selected bibliography