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Biomedical subjects

L F Dietlein

Publications and source records attributed to L F Dietlein.

11 recordsLinked to original sources
PubMed1990

Medical considerations for extending human presence in space.

The prospects for extending the length of time that humans can safely remain in space depend partly on resolution of a number of medical issues. Physiologic effects of weightlessness that may affect health during flight include loss of body fluid, functional alterations in the cardiovascular system, loss of red blood cells and bone mineral, compromised immune system function, and neurosensory disturbances. Some of the physiologic adaptations to weightlessness contribute to difficulties with readaptation to Earth's gravity. These include cardiovascular deconditioning and loss of body fluids and electrolytes; red blood cell mass; muscle mass, strength, and endurance; and bone mineral. Potentially harmful factors in space flight that are not related to weightlessness include radiation, altered circadian rhythms and rest/work cycles, and the closed, isolated environment of the spacecraft. There is no evidence that space flight has long-term effects on humans, except that bone mass lost during flight may not be replaced, and radiation damage is cumulative. However, the number of people who have spent several months or longer in space is still small. Only carefully-planned experiments in space preceded by thorough ground-based studies can provide the information needed to increase the amount of time humans can safely spend in space.

Adaptation, Physiological↗
PubMed1983

Spaceflight and the telltale heart.

Cardiac arrhythmias have not been a common occurrence during manned spaceflights. Cardiovascular deconditioning, on the other hand, is a universal finding both during and after exposure to microgravity. Exercise capability is reduced only in the immediate postflight period as is cardiac output. These adaptive changes do not impair crew health or their ability to perform effectively in weightless flight. We believe that these effects are mediated by a decreased effective circulating blood volume and that they are completely reversible. In any case, an effective countermeasure is available to obviate or mitigate any untoward deconditioning effects on deorbit and return to Earth's gravity.

Adaptation, Physiological↗
PubMed1976

Biomedical results of the Skylab Program.

Skylab, the fourth in a logical sequence of USA manned space flight projects following Mercury, Gemini and Apollo, presented life scientists with their first opportunity for an in-depth study of man's response to the space environment. Extensive medical investigations were undertaken to increase our understanding of man's adaptation to the space environment and his readaptation to gravity upon return to earth. The flight durations of the three Skylab missions were progressively increased from 28 days to 59 days and, finally, 84 days. The results of these investigations of the various body systems clearly demonstrated that man can adapt to zero gravity and perform useful work during long-duration space flight. However, definite changes (some unexpected) in the vestibular, cardiovascular, musculo-skeletal, renal and electrolyte areas were documented. The most significant were: the occurrence of space motion sickness early in the missions; diminished orthostatic tolerance, both in-flight and post-flight; moderate losses of calcium, phosphorus and nitrogen; and decreased tolerance for exercise post-flight. The mechanisms responsible for these physiological responses must be understood and, if necessary, effective countermeasures developed before man can endure unlimited exposure to space flight.

Adaptation, Physiological↗
PubMedDate not supplied

U.S. manned space flight: the first twenty years, a biomedical status report.

In the last 20 years, the biomedical problems facing man in space have been brought into sharper focus. Space motion sickness is presently our most serious problem. Its etiology remains obscure, but the "sensory conflict" theory appears most plausible. No valid predictive tests of susceptibility exist and presently we must rely on medication for prevention or mitigation of symptoms. Adaptation/biofeedback techniques may prove useful. Cardiovascular "deconditioning" may be effectively attenuated by use of anti-g suits or plasma expanding techniques. Recent bedrest simulation studies would seem to indicate that concerns about chronically elevated central venous pressure during space flight are unfounded. The loss of red cell mass in space flight appears to be self-limited, independent of mission duration, and not of clinical concern, based on recent Soviet experiences. And finally, clodronate, a new diphosphonate effective in preventing hypercalciuria and negative calcium balance in normal human bedrested subjects, may prove effective in preventing or lessening skeletal mineral loss in space.

Adaptation, Physiological↗
PubMedDate not supplied

[Future thrusts in life sciences experimentation in space (USA)].

The major physiological problem areas confronting man in space are reviewed and major research questions that remain to be answered are identified. The need for thorough ground-based studies prior to the acquisition of inflight data is emphasized. Future experiments are seen to focus on mechanistic questions and on the development of preventive measures to disturbances in neurophysiology, cardiovascular physiology, skeletal physiology and radiobiology since these areas have highest priority in future manned spacecraft operations.

Animals↗