Central and coronary circulation of the normal man during orthostatic and lower body negative pressure tests.

The effects of the tilt test (at 60-70 degrees for 20 min) and LBNP test (at -30 and -60 mm Hg for 20 min each) on the basic parameters of central circulation (15 test subjects) and coronary circulation (11 test subjects) were investigated. The study was performed using thermistor-equipped catheters implanted into the pulmonary artery and coronary sinus and Teflon catheters implanted into the brachial artery. In the study, the basic parameters of central circulation (pressure in the right atrium and pulmonary artery, transmural pressure in these compartments, cardiac index, stroke index, etc.

Coronary circulation of the healthy man exposed to tilt tests, LBNP, and head-down tilt.

The effect of tilt (head-up and head-down) tests, LBNP tests, and 7-d head-down tilt (at -15 degrees) on coronary circulation was investigated in healthy male volunteers. Catheters were implanted into the coronary sinus and brachial artery. The Ganz catheter in the coronary sinus was used to measure volume flow in the area (constant thermodilution), pressure, and to withdraw samples of outflowing blood for biochemical analysis (acid-base equilibrium and oxygenation).

Effects of various countermeasures against the adverse effects of weightlessness on central circulation in the healthy man.

The effect of lower body negative pressure, local negative pressure below the knee joint, and both pneumatic and mechanical occlusion cuffs at the upper third of the femur on central circulation, oxidative metabolism, and acid-base equilibrium of blood was studied on eight healthy male volunteers with doublelumen Swan-Ganz flow-directed thermodilution catheters implanted for 7 d into the pulmonary artery. The counter-measures against the adverse effects of weightlessness were used in two regimens: regimen I at -30, -50, +40 torr and regimen II at -60, -100, and +60 torr. The parameters were recorded in recumbency, during the head up tilt at 70 degrees for 15 min, and then during the head-down tilt at -20 degrees for 60 min.

[Action on water-salt metabolism as a prophylactic method in orthostatic intolerance in crew members of the 2d expedition of the Saliut-1 station].

The water-salt supplement developed in ground-based experiments in order to increase human tolerance to LBNP and orthostatic tests was recommended to be given to the crewmembers at the final stage of the second expedition of Salyut-4. On the 53rd flight day, concomitantly with an intake of 4.0 g sodium chloride and 900-1200 ml water, an LBNP test was carried out to assess the effectiveness of this supplement, to select its optimal doses and to clarify individual responses.

[Kaliuretic function of the kidneys in humans with different degrees of motor activity and at bed rest].

The kaliuretic function of the kidneys was studied in 12 healthy test subjects during the 49-day head-down tilting (--4 degrees). The results suggest that the selection of optimal exercises and dietary potassium intake may prevent changes in the potassium metabolism and the renal kaliuretic function both during bed rest and weightlessness as well as facilitate a rapid recovery of potassium homeostasis on return to Earth.

[Substantiation of a set of preventive measures applicable to the flight missions of the Saliut orbital station].

The paper describes the effect of exercises, LBNP, controlled water and salt consumption, and drugs used as countermeasures against cardiovascular deconditioning during prolonged (2--7 weeks) head-down bed rest. Each of the above countermeasures applied separately had a limited effect. The use of a combination of exercises, LBNP and water-salt supplements at the final stage of the bed rest experiment made it possible to prevent entirely deterioration of work capacity and decrease of orthostatic tolerance of the test subject.

[Use of the method of selective catheterization of the heart and major vessels in biomedical research with the participation of healthy persons].

The paper discusses the application of direct techniques to the study of circulation--catheterization of the heart and central vessels in biomedical experiments with the participation of healthy volunteers and during examinations of pilots, athletes, etc. The experiments showed high informativeness and reliability of the techniques and demonstrated their applicability to the study of gravity effects on the circulation and metabolism of different organs of healthy men as applied to aerospace and clinical medicine. These investigations allow clinical modelling of hemodynamic and metabolic changes that may develop in various organs and tissues in weightlessness, development of pathogenetically substantiated countermeasures against its adverse effects, formulation of certain requirements for artificial organs whose function should be as close as possible to that of natural organs of a healthy man.

[Evaluation of the effectiveness of electrostimulation of the muscles in preventing disorders related to prolonged limited motor activity in man].

The purpose of the experiments was to evaluate electrostimulation and physical exercises as countermeasures against the adverse effects of diminished motor activity of man in space flight. Electrostimulation of muscles increased their strength and tolerance to static loads, prevented their atrophy; it did not, however, prevent the cardiovascular system deconditioning. Physical exercises used in combination with muscle electrostimulation maintained the cardiovascular system conditioning.

Preliminary results of medical investigations during manned flights of the Salyut 4 orbital station.

In 1975 the Soviet Union performed two manned flights on board the orbital station Salyut 4. The first mission of 30 days was flown by A. A.

Antiorthostatic hypokinesia as a method of weightlessness simulation.

Physiological effects seen in eight test subjects during a 5-d bedrest experiment in the head-down position (0,-4,-8,-12degrees) were studied. It was shown that the antiorthostatic hypokinesia at -12degrees could reproduce physiological responses shown by space crewmembers more closely than recumbent bedrest. Our observations help to stimulate an acute stage of human adaptation to the weightless state and to assess the part played by gravity-induced blood redistribution in the development of physiological changes.

Physiological effects induced by antiorthostatic hypokinesia.

The main purpose of the present investigation was to reproduce some physiological reactions in the sensory system which are similar to those observed during the first day of the adaptation to weightlessness. This was achieved by a 5-day bed rest experiment during which the test subjects were kept in the antiorthostatic position at angles of 0 degrees, -4 degrees, -8 degrees, -12 degrees. Our investigations allowed simulation of the acute stage of adaptation to weightlessness and assessment of gravity-induced blood redistribution in the development of the above physiological reactions.

Effects of muscle electrostimulation during simulated weightlessness.

In a 45-day experiment test subjects were exposed to bed rest with their heads down at -4 degrees C. Twice a day their muscles of the stomach, back, femur, and shin were stimulated with electric current for 25-30 min. The value of muscle tension was close to their maximum voluntary contraction.

Functional insufficiency of the neuromuscular system caused by weightlessness and hypokinesia.

The results of study of the crew members of the spaceships Soyuz are described, and the effects of weightlessness on reflex excitability, muscular tone and muscle contractibility discussed. A certain decrease in postural muscular tone and strength, increase in reflex excitability at rest and increase in bioelectric activity of muscles at work has been found in the cosmonauts after their stay in a weightless environment. The circumference of the lower extremities decreased.

Effects of an 18-day flight on the human body.

During their flight on board the Soyuz 9 A.G. Nikolayev and V.