European isolation and confinement study. Blood pressure, volume-regulating hormones, and electrolytes.

In the ISEMSI confinement experiment we observed three main reactions concerning blood volume regulation: first, a stress activation produced by the high workload that the subjects had to accomplish, both before the isolation period and during the two first weeks of isolation; second, a typical defense reaction to the environment occurred, at least during the two initial days of isolation and later perhaps between crew members themselves; and third, a change in blood volume regulating hormone levels may have been the result of the increase of sympathetic system activity and of dehydration. Confinement is certainly a good and valid method to simulate space station life (with the absence of weightlessness). So, it is interesting to use these confinement studies to perform biological and physiological experiments to obtain greater knowledge, but also to prepare and validate new scientific protocols or new scientific equipment suitable for spaceflights. Even more so, confinement is a good way to prepare and train crew members for long-term space missions. It would seem desirable to confirm the scientific results obtained during the ISEMSI campaign, and especially those for the regulation of the blood volume. This will be done during the next confinement experiment, called EXEMSI, in which four subjects will be subjected to 60 days of confinement.