JOINT NASA-ESA-DARA STUDY - PART 3 - EFFECTS OF CHRONICALLY ELEVATED CO2 ON MENTAL PERFORMANCE DURING 26 DAYS OF CONFINEMENT

Background: Short-term exposures to increased CO2 concentrations in br eathing air up to 5% are assumed to have only negligible behavioral ef fects. In the present study it was examined to what extent prolonged e xposures to moderately elevated levels of CO2 in the ambient air affec t human performance. Method: During two phases of 26 d of confinement in a diving chamber a group of four subjects was exposed to two differ ent levels of CO2 (0.7% and 1.2%). Cognitive, visuo-motor, and time-sh aring performance were assessed repeatedly before, during, and after t he exposure by means of a task battery including grammatical reasoning , memory search, unstable tracking, and dual tasks. In addition, subje ctive workload and mood ratings were collected. A second group of four subjects served as a control group who performed the different tasks on the same 26-d lime schedule without being exposed to confinement an d elevated CO2. Results: During exposure to 0.7% CO2 only tracking per formance was slightly disturbed compared with baseline levels, whereas performance of the control group remained stable. The time course of this effect suggested that it was related to chamber adaptation rather than to increased levels of CO2. During exposure to 1.2% CO2, trackin g performance again was significantly impaired. In contrast to the low er exposure condition, the time course of this effect appeared to be r elated to the CO2 load and covaried with a loss of subjective alertnes s. Conclusions: The study indicates that at least visuomotor performan ce might be affected by CO2 concentrations in the ambient atmosphere a s small as 1.2% if subjects are chronically exposed to these concentra tions in a confined environment. The strength of these effects, howeve r, does not appear to be of operational relevance.