D-04: Circadian Rhythms and Stress Under Different CO2-Concentrationsand Confinement Conditions. D-10: Monitoring of Activity-Rest Cycle Under Different CO2-Concentrations and Confinement Conditions.

Kurzfassung

In four subjects, the effects of elevated CO2-concentrations (0.7 kPa versus 1.2 kPa) on the circadian system and the activity-rest cycle were investigated during consecutive 26 days (under each condition). Circadian parameters were assessed by continuous recording of body temperature and by the determination of excretion rates of cortisol, 6-hydroximelatoninsulfate and catecholamines at 3-h intervals during wake. These measurements were conducted on three consecutive days 4 times during the two campaigns. Non-dominant wrist activity was moni-tored throughout both study phases. Daily means of activity showed significant differences between the two study conditions (with lower values during the 1.2 kPA condition), but these differences only oc- curred during day-time, whereas during sleep activity levels remained the same. Diurnal mean and circadian amplitude of the temperature rhythm was also significantly lower during the 1.2 kPA condition. The humoral parameters are not available yet. Since some circadian data are still in the process of analysis, conclusions must be prelimina- ry. The lower daily mean and circadian amplitudes of temperature du- ring the highter CO2-level can be explained by lower physical activi-ty that was monitored under this level, i. e. a masking effect. We hesitate to explain the lower activity as a response to the changed CO2-concentration. More probably, subjects became so acquainted with the procedures of the study protocol during the second study phase (1.2 kPA CO2) that they did not need similar effort to conduct the tasks as during the first phase. The activity level during sleep which was the same during the two phases may support this conclusion.