Sensitivity of the respiratory regulatory apparatus to CO2 under simulated space flight conditions

: Using the rebreathing method, CO2 sensitivity of the respiration regulation system was investigated during a year-long enclosure study and head-down tilt tests of varying duration (up to 120 days). During the exposures CO2 and H+ were built up in the body. In the course of the enclosure study CO2 sensitivity was reduced. During bed rest experiments this parameter changed differently: it increased on day 7 and significantly decreased on days 55 to 100. These findings show that respiration regulation may vary markedly and indicate that it is worthwhile to carry out similar investigations in an actual space flight.