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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Measurements, modeling, control and simulation - as applied to the human left ventricle for purposeful physiological monitoring.

Interdisciplinary engineering research effort in studying the intact human left ventricle has been employed to physiologically monitor the heart and to obtain its 'state-of-health' characteristics. The left ventricle was selected for this purpose because it plays a key role in supplying energy to the body cells. The techniques for measurement of the left ventricular geometry are described; the geometry is effectively displayed to bring out the abnormalities in cardiac function. Methods of mathematical modeling, which make it possible to determine the performance of the intact left ventricular muscle, are also described. Finally, features of a control system for the left ventricle for predicting the effect of certain physiological stress situations on the ventricle performance are discussed.

Ghista, D. N.↗
NASA NTRS1972

Liquid breathing - Prevention of pulmonary arterial-venous shunting during acceleration.

Dependent pulmonary atelectasis, arterial-venous shunting, and downward displacement of the heart caused by the gravitational-inertial force environment were prevented in dogs breathing oxygenated liquid fluorocarbon in a whole-body water-immersion respirator. Partial closure of the major airways during part of the expiratory phase of liquid respiration was a significant problem initially but was minimized in subsequent studies.

Sass, D. J.↗
NASA NTRS1972

Cardiac beta-adrenergic receptors and coronary hemodynamics in the conscious dog during hypoxic hypoxia.

The mechanisms by which acute hypoxia (10% and 5% oxygen) mediates changes in coronary blood flow and cardiac function were investigated in the conscious dog. When the dogs breathed hypoxic gas mixtures through a tracheostomy, both arterial and coronary sinus oxygen tensions were significantly decreased. With 5% oxygen, there were significant increases in heart rate (25%), maximum left ventricular dP/dt (39%), left circumflex coronary artery blood flow (163%), and left ventricular oxygen consumption (52%), which were attenuated by beta-adrenergic blockage with propranolol. When electrical pacing was used to keep the ventricular rate constant during hypoxia, there was no significant difference in coronary blood flow before and after beta blockade. Beta-adrenergic receptor activity in the myocardium participates in the integrated response to hypoxia although it may not cause active vasodilation of the coronary vessels.

Erickson, H. H.↗
NASA NTRS1972

Circadian rhythms of visual accommodation responses and physiological correlations.

Use of a recently developed servocontrolled infrared optometer to continuously record the state of monocular focus while subjects viewed a visual target for which the stimulus to focus was systematically varied. Calculated parameters form recorded data - e.g., speeds of accommodation to approaching and receding targets, magnitude of accommodation to step changes in target distance, and amplitude and phase lag of response to sinusoidally varying stimuli were submitted to periodicity analyses. Ear canal temperature (ECT) and heart rate (HR) rhythms were also recorded for physiological correlation with accommodation rhythms. HR demonstrated a 24-hr rhythm, but ECT data did not.

Murphy, M. R.↗
NASA NTRS1972

Autonomic control of cardiac function and myocardial oxygen consumption during hypoxic hypoxia.

Investigation in 19 conscious dogs of the importance of the sympathetic nervous system in the coronary and cardiac response to altitude (hypoxic) hypoxia. Beta-adrenergic blockade was used to minimize the cardiac effect associated with sympathetic receptors. It is shown that the autonomic nervous system, and particularly the sympathetic nervous system, is responsible for the increase in ventricular function and myocardial oxygen consumption that occurs during hypoxia. Minimizing this response through appropriate conditioning and training may improve the operating efficiency of the heart and reduce the hazard of hypoxia and other environmental stresses, such as acceleration, which are encountered in advanced aircraft systems.

Erickson, H. H.↗
NASA NTRS1972

Cardiovascular responses to glucagon - Physiologic measurement by external recordings.

Assessment by noninvasive polygraphic techniques of the cardiovascular responses of normal subjects to intravenous injections of glucagon and glucagon diluent. A blinding procedure which eliminated observer bias was used during the reading of tracings. Analysis of group results showed that glucagon provoked uniformly significant changes, including increase in heart rate, blood pressure, pressure-rate product, and ejection time index, and decrease in prejection period, mechanical and electromechanical systole, left ventricular ejection time, and the ratio PEP/LVET. The principal results correlated well with those of previous studies of the hemodynamic effects of glucagon.

Byrne, M. J.↗
NASA NTRS1971

Tissue enzyme studies in Macaca nemestrina monkeys.

Total enzyme activities in fresh tissue specimens from major organs of Macaca nemestrina were analyzed for lactic dehydrogenase (LDH), creatine phosphokinase (CPK), and aldolase. The concentration of these enzymes varied among the different tissue with skeletal muscle, heart, and brain having the highest activities. LDH isozymes determinations for the various tissues were also made. The spectrum of LDH isozyme distribution appears to be quite specific and characteristic for at least some of the tissues analyzed.

Hubbard, R. W.↗
NASA NTRS1972

Evaluation of the pulse-contour method of determining stroke volume in man.

The pulse-contour method for determining stroke volume has been employed as a continuous rapid method of monitoring the cardiovascular status of patients. Twenty-one patients with ischemic heart disease and 21 patients with mitral valve disease were subjected to a variety of hemodynamic interventions. The pulse-contour estimations, using three different formulas derived by Warner, Kouchoukos, and Herd, were compared with indicator-dilution outputs. A comparison of the results of the two methods for determining stroke volume yielded correlation coefficients ranging from 0.59 to 0.84. The better performing Warner formula yielded a coefficient of variation of about 20%. The type of hemodynamic interventions employed did not significantly affect the results using the pulse-contour method. Although the correlation of the pulse-contour and indicator-dilution stroke volumes is high, the coefficient of variation is such that small changes in stroke volume cannot be accurately assessed by the pulse-contour method. However, the simplicity and rapidity of this method compared to determination of cardiac output by Fick or indicator-dilution methods makes it a potentially useful adjunct for monitoring critically ill patients.

Alderman, E. L.↗
NASA NTRS1972

Use of implantable telemetry systems for study of cardiovascular phenomena.

Preliminary observations of cardiovascular function have been made in four chimpanzees using multichannel implantable units. Measurements of right- and left-sided pressures were periodically made in these animals over a four-month period, including continuous observations for selected 24-hour periods. Pressures recorded with animals in an awake, unanesthetized, unrestrained state were much lower than pressures reported for restrained animals in similar situations. Diurnal variations of pressure tended to occur, but were not as clear-cut as those reported to occur for humans. The ability to implant a transmitter chronically and receive useful multichannel information in the chimpanzee encourages the future use of such implant devices as part of the control system for an artificial heart or directly for use in man.

Sandler, H.↗
NASA NTRS1972

Effects of stress upon psychophysiological responses and performance following sleep deprivation

The usefulness of psychological and physiological variables in predicting performance under stress of 48 hours of sleep deprivation was investigated. Performance tests, with subjects of different ego strength personalities, in concept acquisition, reading comprehension, word association, word memory, and anagrams were conducted, and physiological measurements of (1) the phasic and tonic electrodermal, (2) galvanic skin response, (3) thermal skin resistance, (4) heart rate, (5) respiration, and (6) plethysmographic finger pulse volumn were recorded. It was found that the changes in the pattern of performance were the result of testing subjects at times when they would normally be sleeping, and that sleep deprivation longer than 48 hours must be maintained to produce changes in simple or well learned tasks.

Roessler, R.↗
NASA NTRS1973

Cardiac R-wave detector with automatic sensitivity control

An electronic circuit that automatically changes its sensitivity was developed for detecting the bioelectric signal resulting from activation of the heart's ventricles. Regulation of sensitivity was accomplished with two feedback channels that maintain the sensitivity level between an upper and a lower limit. These limits are proportional to the R-wave amplitude. Tests on an experimental circuit demonstrated a capability to reject unwanted signal noise, illustrated difficulties encountered without sensitivity control, and presented closed loop transients which occurred for step changes in R-wave amplitude.

Gebben, V. D.↗
NASA NTRS1969

Experiences with physical conditioning programs in middle-aged men

Long term effects of physical exercise and conditioning in the prevention and treatment of coronary heart disease are studied. Some aspects of the problem are outlined and difficulties encountered in a group of middle aged business executives using a carefully prescribed, but non-regimented and loosely supervised conditioning program employing commonly used forms of exercise (bicycling and jogging), are described.

Schuster, B.↗
NASA NTRS1970

Dynamic EKG Study

The use of the dynamic EKG study as a part of periodic health examination is considered to be a valuable complement to other forms of stress testing with its ability to detect abnormal heart responses to stress stimuli. It is believed that statistical correlations of dynamic EKG findings with physical examination results contribute greatly to the understanding of cardiac abnormalities.

Fleck, R. L.↗
NASA NTRS1970

An Exercise Prescription Intervention Program with Periodic Ergometric Grading

A long term exercise prescription type of physical conditioning program has been available to executive personnel of the NASA Manned Spacecraft Center for the past two years. Periodic ergometric testing with a heart rate controlled, automatically programmed, bicycle ergometer is used to follow the individual's progress and appropriately alter his exercise prescription from time to time. Such a program appears feasible, and acceptance is excellent, dropout rates small and periodic testing participation good. Subjects training diligently can maintain satisfactory levels of conditioning.

Owen, C. A.↗
NASA NTRS1970

The Value of Continued Followup in a Preventive Medicine Program

Continued monitoring of hypertension and cholesterol levels in NASA employees by regularly scheduled medical examinations prevents an increase in employee disability and cardiovascular mortality rates. Adequate therapeutic control for younger hypertensive employees is demonstrated by records on mortality and heart diseases over a period of 28 months. It confirmed the importance of systolic blood pressure as diagnostic tool for the inherent risk factor. The prevalence of additional coronary risk factors among employees with hypercholesterolemia is considerably less than in employees with hypertension.

Villafana, C.↗
NASA NTRS1970

Flight Crew Health Maintenance

The health maintenance program for commercial flight crew personnel includes diet, weight control, and exercise to prevent heart disease development and disability grounding. The very high correlation between hypertension and overweight in cardiovascular diseases significantly influences the prognosis for a coronary prone individual and results in a high rejection rate of active military pilots applying for civilian jobs. In addition to physical fitness the major items stressed in pilot selection are: emotional maturity, glucose tolerance, and family health history.

Gullett, C. C.↗
NASA NTRS1971

Stress Studies at Kennedy Space Center: a Backward and Forward Look

Possible relationships between occupational and other stresses on ischemic heart disease are explored. Three procedures were used: (1) double master 2-step test, (2) dynamic ECG technique using avionics equipment, and (3) submaximal stress testing with Marco bicycle ergometer.

A. I. Decker↗
NASA NTRS1972

The NASA-USPHS Health Evaluation and Enhancement Program

An exercise program was initiated to assess the feasibility of an on the job health evaluation and enhancement program, as well as to identify the factors which influenced volunteering, adherence, and effectiveness of the program. The program was utilized by 237 of the 998 eligible Federal employees, with a mean attendance of 1.3 days per week. Those who volunteered perceived a need for increased physical activity, felt they had sufficient time to participate, and derived subjective as well as objective benefits. Significant improvements were found in heart rate response to the standard exercise test, body weight, skinfold measurements, and triglycerides. A consistent relationship was found between subjectively reported effects of the program on work, health habits, and behavior, and improvement in cardiovascular function, based on treadmill performance. Numerous personal and programmatic factors influencing volunteering and participation were identified.

Durbeck, D. C.↗