PHYSIOLOGICAL AND PSYCHOLOGICAL EFFECTS ASSOCIATED WITH HIGH-CARBON DIOXIDE LEVELS IN HEALTHY-MEN

Background: Perception of CO2 in ambient air may be of fundamental imp ortance to the health, safety, and job performance of persons occupati onally exposed to increased levels of CO2. Few studies have examined t he perceptual responses to inhaled CO2 at levels between 6-10%. Hypoth esis: We hypothesized that healthy, highly-active men would be able to determine the difference between 6% and 8% CO2 concentrations. Method s: Thirty-two male students (21 +/- 1 yr) served as subjects. Experime ntal trials (counterbalanced design) included breathing air (control, 21% O-2, 79% N-2), 6% CO2 (21% O-2, 73% N-2), and 8% CO2 (21% O-2, 71% N-2) conditions. The Body Sensations Questionnaire (BSQ) was complete d twice during each trial. Results: End tidal CO2 (FETCO(2)) and BSQ v alues increased (p < 0.05) as a function of the percentage of inhaled CO2. Respiratory rates during the 8% trial were greater (p < 0.05) tha n control and 6% CO2 trial measures. BSQ scores were significantly cor related with FETCO(2) and respiratory rate measures during the 6% and 8% CO2 conditions. Conclusions: We conclude that these subjects recogn ized their exposure to both the 6% and 8% CO2 concentrations, and thei r responses were more profound during the 8% CO2 condition.