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The article includes excerpts from The Bioethic Rules of Research With Humans and Animals that have established on analysis of national and international bioethic guidelines for biomedical research with the use of humans and animals and are a part of the ISS human use guidelines.

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The paper deals with ethic concerns of biomedical research involving human subjects aimed at mitigating risks for and raising the effectiveness of humans in extreme environments. Cited are the main principles of the Nuremberg Code, Helsinki Declaration, Convention of the European Council on Bioethics and other international and national documents regulating ethic implementation of research with participation of human subjects. The 6-year experience of the Bioethics Commission convened at SRC RF--IBMP is summarised.

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The article describes the procedure of determining methane and some organic trace elements in expired air during simulated "dive" in a hyperbaric chamber. Partial pressures of methane breathed out by divers in 29 experiments are reported. Concentrations of 8 trace organic components have been measured in the expired air of two divers. The results obtained show that expired methane increases by 3-10 times during simulated descent down to 80-115 m.

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Reactions of external respiration on catheterization of main blood vessels were studied in healthy subjects following 12 hr and 5-6 day immersion. The purpose of the investigation was to detect respiratory signs of hyperemia in pulmonary circulation under these conditions. Results of the investigation were compared with the data of great vessel catheterization in patients of a cardiological clinic afflicted with cardiac diseases with lung hyperemia and lung tissue hyperhydration. The results obtained failed to confirm suppositions about elevated blood filling of the lung and a possible increase of lung tissue hydration during water immersion. Catheterization of great vessels in patients and healthy subjects in most cases leads to an increase of respiratory minute volume. In patients with cardiac diseases the respiratory minute volume grew with an adequate rise in breathing rate, respiratory volume and gas exchange parameters unaltered; this suggested excessive blood filling of the lung and resulting higher respiratory resistance. After immersion the healthy subjects displayed an utterly different pattern, i.e. the growth of their respiratory minute volume was provided exclusively by the growth of respiratory volume while breathing rate did not change and gas exchange increased. These observations were considered an evidence of hyperemia and hyperhydration of pulmonary tissue.

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Data on a possible use of hydrogen as a part of the breathing mixtures during deep diving are presented; advantages and disadvantages of hydrogen application in the undersea research and diving practice are evaluated. Perspectives and trends with respect to a safe hydrogen use under high pressure in combination with oxygen and other inert gases are discussed.

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Hyperbaric neon-oxygen mixture has been studied for the effect of its high density under pressure of 41 ata on basic physiological functions of human organism. Typical changes of the cardiorespiratory system and tissue respiration parameters are revealed. Changes in physical working capacity are shown. Exposure to gaseous medium of high pressure and density is accompanied by the development of some compensatory-adaptive reactions. The possibility to perform mid-hard physical work is attained with overstrain of respiration and circulation function.

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Central and peripheral hemodynamics was investigated in 16 essentially healthy volunteers who performed a routine tilt test or a tilt test in water immersion. Unlike tilt tests carried out before water immersion, the supine to up-right transfer in water did not change cardiac rhythm, cardiac output, leg blood flow or other circulation parameters. The fact that there are no posture-related circulation changes in water immersion suggests that the horizontal and upright positions in water can be viewed as hemodynamically similar.

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Seven healthy volunteers were exposed to head-down tilt at -15 degrees for 5 h. Before and after exposure they exercised on a bicycle ergometer in the supine and seated positions. During the study their respiration function, gas exchange, and arterialized blood parameters were measured. It was found that after exposure the physical aerobic performance diminished. The changes detected suggest that a lower exercise tolerance can be caused not only by a decreased circulating blood volume but also by increased energy expenditures of the cardiorespiratory system itself.

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Simultaneous measurements by the Fick direct method and the Kubicek rheographic method of cardiac output of 20 men with ischemic heart disease have shown that both methods are well correlated (r = 0.76, k = 0.92, n = 41). The reproducibility of the Kubicek data was slightly better than the Fick data (on the average +/- 6% instead of +/- 9-10%). An attempt of increasing the correlation of the Kubicek data with the Fick data by correcting the specific resistance with respect to the hematocrit data and the chest perimeter failed. In order to provide the necessary accuracy of the Kubicek method, it is required that the procedure be stringent and the five variables in the formula for calculating cardiac output be precisely measured. The cardiac output values determined simultaneously by the Kubicek method and by x-ray contrast ventriculography showed a better correlation (r = 0.88, k = 0.97, n = 15).

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In 1977-1981 the Soviet Union launched 18 manned space missions under the Salyut-6--Soyuz program which included five flights of prime crews for 96, 140, 175, 185, and 75 days and eleven flights of visiting crews. Altogether 30 cosmonauts, including 9 crewmembers from other than the USSR socialist countries, took part in the program. Emphasis was given to the medical investigations, since their purpose was not only to assess the health status of the crewmembers and to investigate their responses to prolonged weightlessness, but also to identify the maximum allowable flight time.

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The major goal of biomedical investigations in prolonged (up to 6 months) manned missions was to obtain information about physiological reactions to long-term weightlessness and to carry out detailed clinical, physiological, immunological and anthropometric investigations before, during and after flight. The results obtained give evidence that man can adapt to the prolonged exposure and to maintain good health condition and high work capacity. The changes detected postflight were reversible and disappeared completely within a relatively short time period. The changes were not correlated with the flight duration. The good health condition and high performance inflight were maintained and postflight readaptation was facilitated due to a rational work-rest cycle and specific countermeasures which were modified with respect to the results of regular medical examinations. Salyut-6 medical data have demonstrated that the duration of forthcoming manned missions can be extended.

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The major goal of medical investigations in the USSR longterm (up to 6 months) manned space flights was to accumulate information on human responses to prolonged weightlessness. Before, during and after these flights, detailed clinical, physiological, immunological and anthropometric examinations were conducted. The examinations demonstrated that man may well adapt to long-term space flight, retaining good health and a high work capacity. The changes seen postflight were reversible and disappeared completely after a relatively short readaptation period. Postflight changes did not correlate with the flight duration. A reasonable work-rest cycle and various physiological countermeasures were used, the efficiency of which were substantiated by means of regular medical examinations. These methods helped the cosmonauts to maintain good health status and adequate performance inflight and facilitated their readaptation postflight. Medical investigations performed during the Salyut-6 flights indicate that the duration of manned space flight can be increased.

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The effects of acceleration of different value (up to 2 g) on the level of motion sickness, vestibular and postural reactions to rotation were studied. The experiments were carried out in a centrifuge equipped with a cabin that could be mounted at a different distance from the axis of rotation. Three experimental runs were conducted with a rate of rotation of 15.3 and accelerations values of 1.09, 1.6 and 2.0 g. Vestibular stimulation was produced by head movements of a predetermined number. It was found that with increase in the acceleration value the level of motion sickness decreased and the nystagmic reaction and balance dysfunction enhanced.

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