Postural reactions of circulation and its regulation during simulated weightlessness.

The extention and intensification of space exploration the influence of weightlessness on human organism and the formation of a new level of adaptation. The studies of blood circulation is very important because of frequent occurrence of cardiovascular disorders in the middle age subjects. In connection with extension and intensification of space exploration the influence of weightlessness on human organism and the formation of a new level of adaptation mechanisms acquires a special significance. The data obtained in recently undertaken model experiments and also during space flights indicate that weightlessness in many ways affects various physiological systems of organism, and first of all cardiovascular system with the development of reflex, humeral and metabolic reactions. It also indicates, that the changes in functioning of cardiovascular system brings about the disruption of its regular responses, which is foremost expressed in decreased antigravitational response, which manifests itself in lowered orthostatic stability. It is worth mentioning, that the changes during previous investigations of haemodynamics were mainly carried out with the subjects under forty, therefore age related specific features of blood circulation system response are described in a few articles. The studies of the kind are especially important because of frequent occurrence of cardiovascular disorders such as heart and brain vessels atherosclerosis, hypertension in the middle age, which can to a great extent complicate and affect the "acute" period of adaptation to weightlessness and readaptation process.

[Posture-related changes in hemodynamics in humans after administration of sidnocarb and its combination with obsidan]. / Kharakter postural'nykh izmenenii gemodinamiki cheloveka pri primenenii sidnokarba i ego kombinatsii s obzidanom.

Experiments were carried out to study the effect of sydnocarb 3-(beta-phenylisopropyl)-N-phenylcarbamoyl-sydnonimine), a stimulant of mental and physical performance, and its combination with obsidan, a beta-adrenoblocking agent, on the central and peripheral hemodynamics during a head-up test (+75 degrees) after a 6-hour head-down tilt (-15 degrees). Sydnocarb increased the tone of brain and leg arterioles, left unchanged stroke volume and cardiac output, and decreased the postural increment of heart rate. Sydnocarb (15 mg) combined with obsidan (20 mg) reduced heart rate and its postural increment, increased stroke volume, and increased the tone of resistive vessels, as was also the effect of sydnocarb taken separately.

[Features of the functional capabilities of the bodies of older persons exposed to simulated space flight factors]. / Osobennosti funktsional'nykh vozmozhnostei organizma lits starshego vozrasta pri vozdeistvii modelirovannykh faktorov kosmicheskogo poleta.

In response to simulated space flights cardiovascular and metabolic changes of 86 volunteers, aged 40-49 and 50-56, were similar to those of young people (25-39 years old). In most aged test subjects, the changes produced by 8-day head-down tilt (-8 degrees) and 7-day water immersion were moderate and reversible. This type of variation of the adaptive-compensatory reactions give evidence that aged people have sufficiently high functional capabilities. Nevertheless, 36% test subjects, aged 40-49, and 50% test subjects, aged 50-56, displayed certain features suggesting a reduction of the adaptive-compensatory capabilities (functional reserves) as a result of age-related and atherosclerotic changes of the cardiovascular system.

[Central and regional hemodynamics during LBNP exposure studied by isotopic and impedance methods]. / Izuchenie tsentral'noi i regionarnoi gemodinamiki izotopnym i impedansnym metodami pri vozdeistvii ODNT.

The potential of impedance and isotope (intravenous injections of 131I and 113mIn) methods to study regional and central hemodynamics was investigated on 12 test subjects exposed to LBNP. Both methods demonstrated marked changes in blood filling of the head and the chest, particularly during the first minutes of LBNP tests. This occurred together with a drastic increase in leg blood filling. The close similarity of regional hemodynamic changes detected by the two methods gives evidence that the simple and noninvasive impedance method can be well used for the above studies.

[Prognostic importance of the head-down tilting load]. / Izuchenie prognosticheskoi znachimosti antiortostaticheskoi nagruzki.

The prognostic significance of head-down tilt at -15 degrees and -30 degrees for 6 min at each step was assessed in 40 normal men, aged 22-39. The study of mean values of the maximal amplitude, relative duration of the anacrotic phase, dicrotic and diastolic indices of hemispheric and bimastoidal rheoencephalography as well as of health condition helped to determine cerebral circulation in test subjects with good and moderate tolerance to head-down tilt and to define the criteria of tilt tolerance. The test subjects who showed good tolerance to head-down tilt displayed a simultaneous compensatory increase of the tone of large caliber arteries and arterioles that was accompanied by a noticeable increase in cerebral pulse blood filling at -15 degrees and a moderate increased at -30 degrees as well as the feeling of a slight blood rush to the head. The test subjects who displayed moderate tolerance to head-down tilt showed only an increase in the tone of large caliber vessels; they also exhibited a marked decrease in the tone of arterioles, venules and veins (especially at -30 degrees) which was combined with a significant increase in the cerebral pulse blood filling and an appearance of marked venous waves on rheoencephalograms.

[External respiration and gas metabolism in orthostatic syncopes]. / Vneshnee dykhanie i gazoobmen pri ortostaticheskikh obmorokakh.

Cardiorespiratory reactions to tilt tests were compared in 80 healthy male subjects with an adequate orthostatic tolerance and in 19 subjects who fainted during tilting. They showed significant differences in the gas exchange, hemodynamics, and external respiration. Variations in the heart rate, pulmonary ventilation and the alveolar CO2 tension were most demonstrative. The findings, particularly the lack of the expected decrease o= oxygen consumption in the presyncopal state contribute to the concepts of the pathogenesis of the orthostatic collapse.