Method of Selection of Astronauts Cardiovascular Regulative Function under Simulated Weightlessness

Nowadays, methods and standards for the selection of astronauts'cardiovascular regulative function are getting improved though not yet perfect. A method of—15°head-down tilt in bed for 4h in stead of —2～—6° head down for 1～2 weeks as commonly used by other authors was used in this study. Cardioveascular regulative function and its adaptation to the effects of body fluid redistribution were observed, and individual differences among the subjects were also analysed. Adaptive and unadaptive reactions were differentiated clearly. Reactions resembling the space-adaptation syndrome were found in 13/38 of the subjects within 30～60 min of bed rest when marked changes of heart rate (HR), blood pressure (BP), arteriole compliance (AC), and rheoencephalogram (REG) occurred. It was suggested that blood redistribution during head down tilt not only caused changes in cardiovascular functions, but also induced functional, or even structural changes in the brain, and those who were adapted to this kind of reactions would be more susceptible to space-adaptive-syndrome.The experiment on all of the 13 unadaptive subjects were suspended because of disturbances inautonomic nervous system observed in 30～60 min. All of the 25 adapative subjects could endureover 4h. The same tests were repeated in 12 subjects (7 adapative, 5 unadapative) 2—3 weeks later, and the results were consistent with those of the first experiment perfectly. The results showed that the method of —15° head-down tilt in bed for 1 h could be used in the selection of adptability of human body to microgravity.