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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Mathematical modeling of acute and chronic cardiovascular changes during Extended Duration Orbiter (EDO) flights

The purpose of NASA's Extended Duration Orbiter program is a gradual extension of the capabilities of the Space Shuttle Orbiter beyond its current 7-10 day limit on mission duration, as warranted by deepening understanding of the long-term physiological effects of weightlessness. Attention is being given to the cardiovascular problem of orthostatic tolerance loss due to its adverse effects on crew performance and health during reentry and initial readaptation to earth gravity. An account is given of the results of the application of proven mathematical models of circulatory and cardiovascular systems under microgravity conditions.

White, Ronald J.↗
NASA NTRS1991

Gender-based differences in the cardiovascular response to standing

The cardiovascular responses of men and women to the stand test were compared by measuring respective values for heart rate, blood pressure, stroke volume, cardiac output, and total peripheral resistance during a 5-min supine and a 5-min standing test in ten subjects of each gender. It was found that, while the male and female subjects had similar heart rate values, all other responses exhibited greater changes in men than in women. While differences in the height of the subjects did not account for differences in cardiovascular responses, no mechanism responsible for these differences could be identified.

Gotshall, Robert W.↗
NASA NTRS1991

Cardiovascular adaptation to O-G (Experiment 294) - Instrumentation for invasive and noninvasive studies

Many astronauts returning from space have difficulties regulating blood pressure, some to the point of fainting during quiet standing. Experiment 294 was designed to study this and other cardiovascular effects of adaptation to microgravity and to understand the mechanisms behind it. To accomplish this several cardiovascular variables had to be measured accurately. Heart rate, blood pressure, cardiac output (blood pumped by the heart each minute), stroke volume (blood pumped by the heart with each beat), limb flow, limb compliance, heart size and central venous pressure all had to been recorded during various stresses to understand fully the adaptation to space and the readaptation to earth's gravity. Numerous pieces of equipment were used. Some were purpose-built for the Spacelab mission and others were derived from commercial hardware. Developing spaceflight hardware is challenging and costly, but can lead to significant new information in the unique environment of space.

Buckey, Jay C.↗
NASA NTRS1992

Cardiovascular orthostatic function of Space Shuttle astronauts during and after return from orbit

Routine entry, landing, and seat egress after Space Shuttle flights is observed to be associated with drops in blood pressure and increases in heart rate that indicate that the cardiovascular system is performing at its maximum capacity in a large fraction (30 percent) of the study population. It is not apparent that adequate cardiovascular reserve capacity remains to accommodate unaided emergency egress after either current or extended space flights.

Charles, John B.↗
NASA NTRS1992

Rat cardiovascular responses to whole body suspension - Head-down and non-head-down tilt

Two experiments aimed at examining the versatility of the whole body suspension (WBS) system as a ground-based model for cardiovascular effects of microgravity are described. The first experiment studied heart rate and arterial pressure responses in rats during a 7-day period of head-down tilt (HDT) or nonhead-down tilt (NHDT) and after removal from whole body suspension (WBS). Mean arterial (MAP), systolic, and diastolic pressures increased about 20 percent in HDT rats on the fist day, heart rates were elevated about 10 percent. During postsuspension most cardiovascular parameters returned to presuspension levels. The second experiment evaluated responses to rapid head-up tilt in HDT and NHDT rats. It was observed that, while pulse pressures remained unchanged, MAP, systolic and diastolic pressures, and HR were elevated in HDT and NHDT rats during head-up tilt after one day of suspension. The WBS rats are considered to be useful as a model to better understand responses of rats exposed to microgravity.

Musacchia, X. J.↗
NASA NTRS1991

Cardiovascular adaptation to spaceflight

Data are presented on the rate of adaptation of the human cardiovascular system to conditions of spaceflight, with particular attention given to data obtained during spaceflight in the U.S. Space Shuttle Program. It is pointed out that many of the cardiovascular changes that occurred during spaceflights that lasted from 2 to 11 days can be traced directly to changes in the body fluid volume. The beneficial effects of a fluid loading countermeasure (oral rehydration) and of the supine body position on the heart rate during the spaceflight are demonstrated. It is noted that, after hours or a few days of spaceflight, a state of adaptation is reached, in which the subject is well adapted and appropriately hydrated for the weightless environment. However, the return to the normal gravity of the earth leaves the individual especially sensitive to orthostatic stress.

Charles, John B.↗
NASA NTRS1991

Echocardiographic evaluation of the cardiovascular effects of short-duration spaceflight

Results are presented of echocardiographic investigations and hemodynamic measurements performed on 24 astronauts before and after short-duration (4-5 days) spaceflight, including data on the heart rate, blood pressure, and cardiac volumes. Cardiovascular changes which were found to occur after 4-5 day long spaceflight included decreased the left ventricular end-diastolic volume and the stroke volume indices, with a compensatory increased heart rate and the cardiac output being maintained; in addition, altered total peripheral vascular resistance was found to occur, with an apparent reduction in the ability to augment the peripheral vascular tone upon assuming the standing position. These cardiovascular characteristics normalized within 48 hrs of landing.

Mulvagh, Sharon L.↗
NASA NTRS1991

Cardiovascular physiology in space flight

The effects of space flight on the cardiovascular system have been studied since the first manned flights. In several instances, the results from these investigations have directly contradicted the predictions based on established models. Results suggest associations between space flight's effects on other organ systems and those on the cardiovascular system. Such findings provide new insights into normal human physiology. They must also be considered when planning for the safety and efficiency of space flight crewmembers.

Charles, John B.↗
NASA NTRS1991

Cardiovascular dynamics during space sickness and deconditioning

We are currently funded by NASA for the project, 'Cardiovascular Dynamics During Space Sickness and Deconditioning.' NASA has given priority to the investigation of two problems encountered in the long-term space flights currently being planned: (1) space motion sickness; and (2) cardiovascular deconditioning. We have proposed to use spectral and nonlinear dynamical analysis of heart rate data to quantify the presence of these problems and to evaluate countermeasures against them.

Goldberger, Ary L.↗
NASA NTRS1993

Characterization of fluid physics effects on cardiovascular response to microgravity (G-572)

The recognition and understanding of cardiovascular adaptation to spaceflight has experienced substantial advancement in the last several years. In-flight echocardiographic measurements of astronaut cardiac function on the Space Shuttle have documented a 15 percent reduction in both left ventricular volume index and stroke volume with a compensatory increase in heart rate to maintain cardiac output. To date, the reduced cardiac size and stroke volume have been presumed to be the consequence of the reduction in circulating fluid volume following diuresis and other physiological processes to reduce blood volume within a few days after orbital insertion. However, no specific mechanism for the reduced stroke volume has been elucidated. The following investigation proposes the use of a hydraulic model of the cardiovascular system to examine the possibility that the observed reduction in stroke volume may, in part, be related to fluid physics effects on heart function. The automated model is being prepared to fly as a GAS payload. The experimental apparatus consists of a pneumatically actuated, elliptical artificial ventricle connected to a closed-loop, hydraulic circuit with compliance and resistance elements to create physiologic pressure and flow conditions. The ventricle is instrumented with high-fidelity, acceleration-insensitive, catheter-tip pressure transducers (Millar Instruments) in the apex and base to determine the instantaneous ventricular pressures and (delta)P(sub LV) across the left ventricle (LVP(sub apex)-LVP(sub base). The ventricle is also instrumented with a flow probe and pressure transducers immediately upstream of the inflow valve and downstream of the outflow valve. The experiment will be microprocessor controlled with analog signals stored on the FM data tape recorder. By varying the circulating fluid volume, ventricular function can be determined for varying preload pressures with fixed afterload pressure. Pilot experiments on board the NASA KC-135 aircraft have demonstrated proof-of-concept and provided early support for the proposed hypothesis. A review of the pilot experiments and developmental progress on the GAS version of this experiment will be presented.

Pantalos, George M.↗
NASA NTRS1995

Characterization of fluid physics effects on cardiovascular response to microgravity (G-572)

The investigation of cardiovascular adaptation to space flight has seen substantial advancement in the last several years. In-flight echocardiographic measurements of astronaut cardiac function on the Space Shuttle have documented an initial increase, followed by a progressive reduction in both left ventricular volume index and stroke volume with a compensatory increase in heart rate to maintain cardiac output. To date, the reduced cardiac size and stroke volume have been presumed to be the consequence of the reduction in circulating fluid volume within a few days after orbital insertion. However, no specific mechanism for the reduced stroke volume has been identified. The following investigation proposes the use of a hydraulic model of the cardiovascular system to examine the possibility that the observed reduction in stroke volume may, in part, be related to fluid physics effects on heart function. The automated model is being prepared to fly as a Get Away Special (GAS) payload within the next year.

Pantalos, George M.↗
NASA NTRS1992

Rat Cardiovascular Responses to Whole Body Suspension: Head-down and Non-Head-Down Tilt

The rat whole body suspension technique mimics responses seen during exposure to microgravity and was evaluated as a model for cardiovascular responses with two series of experiments. In one series, changes were monitored in chronically catheterized rats during 7 days of Head-Down Tilt (HDT) or Non-Head-Down Tilt (N-HDT) and after several hours of recovery. Elevations of mean arterial (MAP), systolic, and diastolic pressures of approx. 20 % (P less than 0.05) in HDT rats began as early as day 1 and were maintained for the duration of suspension. Pulse pressures were relatively unaffected, but heart rates were elevated approx. 10 %. During postsuspension (2-7 h), most cardiovascular parameters returned to presuspension levels. N-HDT rats exhibited elevations chiefly on days 3 and 7. In the second series, blood pressure was monitored in 1- and 3-day HDT and N-HDT rats to evaluate responses to rapid head-up tilt. MAP, systolic and diastolic pressures, and HR were elevated (P less than 0.05) in HDT and N-HDT rats during head-up tilt after 1 day of suspension, while pulse pressures remained un changed. HDT rats exhibited elevated pretilt MAP and failed to respond to rapid head-up tilt with further increase of MAP on day 3, indicating some degree of deconditioning. The whole body suspended rat may be useful as a model to better understand responses of rats exposed to microgravity.

Musacchia, X. J.↗
NASA NTRS1999

Nutritional Aspects of Crewmembers' Cardiovascular Health Indicated by Dietary Lipids

This summer's project examined the relationships between dietary and physiological factors on serum lipoproteins using data from past United States astronauts. Nutritional assessment was required to determine whether a relationship existed between dietary intake and risk of cardiovascular disease (CVD) in crewmembers. Risk for CVD was assessed by the measurement of preflight, inflight, and postflight serum lipoproteins. The purpose of this project was to evaluate the dietary practices of past crewmembers before and during flight, and to examine their relationship with blood indicators of lipid status. Because of mortality and morbidity associated with CVD, such assessments are critical for the maintenance of astronaut health before, during, and after space flight. It was anticipated that the results from this project would assess the effects space flight and diet have on cardiovascular health, thus, defining the adequacy of the current dietary recommendations during space travel. It was hypothesized that the mean preflight serum lipoproteins compared to mean postflight serum lipoproteins would not be statistically different and that the current inflight diet is adequate in nutrient content, having little or no effect on lipoprotein levels.

Thurston, Marcelle A.↗
NASA NTRS1999

Rodent Studies of Cardiovascular Deconditioning

Changes in blood pressure can occur for two reasons: 1) A decrease in cardiac output resulting from the altered contractility of the heart or through changes in venous filling pressure via the Frank Starling mechanism or; 2) A change in systemic vascular resistance. The observed changes in cardiac output and blood pressure after long term space flight cannot be entirely explained through changes in contractility or heart rate alone. Therefore, alterations in filling pressure mediated through changes in systemic venous capacitance and arterial resistance function may be important determinants of cardiac output and blood pressure after long term space flight. Our laboratory and previous studies have shown the importance of veno-constriction mediated by the carotid sinus baroreceptor reflex system on overall circulatory homeostasis and in the regulation of cardiac output. Our proposed experiments test the overall hypothesis that alterations in venous capacitance function and arterial resistance by the carotid sinus baroreceptor reflex system are an important determinant of the cardiac output and blood pressure response seen in astronauts after returning to earth from long term exposure to microgravity. This hypothesis is important to our overall understanding of circulatory adjustments made during long term space flight. It also provides a framework for investigating counter measures to reduce the incidence of orthostatic hypotension caused by an attenuation of cardiac output. We continue to use hind limb unweighted (HLU) rat model to simulate the patho physiological effects as they relate to cardiovascular deconditioning in microgravity. We have used this model to address the hypothesis that microgravity induced cardiovascular deconditioning results in impaired vascular responses and that these impaired vascular responses result from abnormal alpha-1 AR signaling. The impaired vascular reactivity results in attenuated blood pressure and cardiac output responses to an orthostatic challenge. We have used in vitro vascular reactivity assays to explore abnormalities in vascular responses in vessels from HLU animals and, cardiac output (CO), blood pressure (BP) and heart rate (HR) measurements to characterize changes in hemodynamics following HLU.

Shoukas, Artin A.↗
NASA NTRS1994

Human cardiovascular response to sympathomimetic agents during head-down bed rest: the effect of dietary sodium

Changes in sympathoadrenal function and cardiovascular deconditioning have long been recognized as a feature of the physiological adaptation to microgravity. The deconditioning process, coupled with altered hydration status, is thought to significantly contribute to orthostatic intolerance upon return to Earth gravity. The cardiovascular response to stimulation by sympathomimetic agents before, during, and after exposure to simulated microgravity was determined in healthy volunteers equilibrated on normal or high sodium diets in order to further the understanding of the deconditioning process.

NASA Discipline Number 18-10↗
NASA NTRS1994

Cardiovascular responses to postural changes: differences with age for women and men

The cardiovascular responses to postural change, and how they are affected by aging, are inadequately described in women. Therefore, the authors examined the influence of age and sex on the responses of blood pressure, cardiac output, heart rate, and other variables to change in posture. Measurements were made after 10 minutes each in the supine, seated, and standing positions in 22 men and 25 women who ranged in age from 21 to 59 years. Several variables differed, both by sex and by age, when subjects were supine. On rising, subjects' diastolic and mean arterial pressures, heart rate, total peripheral resistance (TPR), and thoracic impedance increased; cardiac output, stroke volume, and mean stroke ejection rate decreased; and changes in all variables, except heart rate, were greater from supine to sitting than sitting to standing. The increase in heart rate was greater in the younger subjects, and increases in TPR and thoracic impedance were greater in the older subjects. Stroke volume decreased less, and TPR and thoracic impedance increased more, in the women than in the men. The increase in TPR was particularly pronounced in the older women. These studies show that the cardiovascular responses to standing differ, in some respects, between the sexes and with age. The authors suggest that the sex differences are, in part, related to greater decrease of thoracic blood volume with standing in women than in men, and that the age differences result, in part, from decreased responsiveness of the high-pressure baroreceptor system.

Posture/physiology↗
NASA NTRS2005

MRI-Based Computational Fluid Dynamics in Experimental Vascular Models: Toward the Development of an Approach for Prediction of Cardiovascular Changes During Prolonged Space Missions

A priority of NASA is to identify and study possible risks to astronauts health during prolonged space missions [l]. The goal is to develop a procedure for a preflight evaluation of the cardiovascular system of an astronaut and to forecast how it will be affected during the mission. To predict these changes, a computational cardiovascular model must be constructed. Although physiology data can be used to make a general model, a more desirable subject-specific model requires anatomical, functional, and flow data from the specific astronaut. MRI has the unique advantage of providing images with all of the above information, including three-directional velocity data which can be used as boundary conditions in a computational fluid dynamics (CFD) program [2,3]. MRI-based CFD is very promising for reproduction of the flow patterns of a specific subject and prediction of changes in the absence of gravity. The aim of this study was to test the feasibility of this approach by reconstructing the geometry of MRI-scanned arterial models and reproducing the MRI-measured velocities using CFD simulations on these geometries.

Spirka, T. A.↗
NASA NTRS2005

WISE-2005: Integrative Cardiovascular Responses with LBNP during 60-Day Bed Rest in Women

During 2005, 24 women will take part in the Women International Space-simulation for Exploration (WISE). In this paper we report on the first phase that studied 4 Exercise (EX+LBNP), 4 nutrition (NUT), and 4 no countermeasure control (CON) subjects. The EX+LBNP group completed regular exercise on a treadmill inside LBNP, flywheel resistive exercise and static periods of LBNP, and had recovery days. The NUT group received daily protein supplements. Integrative cardiovascular responses were obtained and here we report data for heart rate during LBNP, blood volume and angiotensin 11. LBNP was applied at 0, -10, -20 and -30 mmHg for 2-minutes for each stage. Blood was sampled prebed rest and on HDT-60. After 60-days head down bed rest, HR in the CON group increased by 6.1+/-2.8 bpm at rest and by 20.7+/-5.0 bpm at -30 mmHg LBNP. The EX+LBNP group had increases of 3.6+/-5.6 and 11.6+/-5.4 bpm, while the NUT group HR increased 2.6+/-3.1 and 9.4+/-3.6 bpm. The EX+LBNP group had almost no change in blood volume or plasma angiotensin II from pre-bed rest to HDT60, while both the CON and NUT groups had larger increases in plasma volume and almost double concentrations of angiotensin II. These data show a positive effect in the EX+LBNP group on the heart rate response as well as an unexpected possible benefit in the NUT group. Further studies are required to confirm possible cardiovascular benefits of the protein supplement.

Hughson, R. L.↗