title: Physiological and psychological effects associated with high carbon dioxide levels in healthy men.
abstract: BACKGROUND
  Perception of CO2 in ambient air may be of fundamental importance to the health, safety, and job performance of persons occupationally exposed to increased levels of CO2. Few studies have examined the perceptual responses to inhaled CO2 at levels between 6-10%.
  
  
  OBJECTIVE
  We hypothesized that healthy, highly-active men would be able to determine the difference between 6% and 8% CO2 concentrations.
  
  
  METHODS
  Thirty-two male students (21 +/- 1 yr) served as subjects. Experimental trials (counterbalanced design) included breathing air (control, 21% O2, 79% N2), 6% CO2 (21% O2, 73% N2), and 8% CO2 (21% O2, 71% N2) conditions. The Body Sensations Questionnaire (BSQ) was completed twice during each trial.
  
  
  RESULTS
  End tidal CO2 (FETCO2) and BSQ values increased (p < 0.05) as a function of the percentage of inhaled CO2. Respiratory rates during the 8% trial were greater (p < 0.05) than control and 6% CO2 trial measures. BSQ scores were significantly correlated with FETCO2 and respiratory rate measures during the 6% and 8% CO2 conditions.
  
  
  CONCLUSIONS
  We conclude that these subjects recognized their exposure to both the 6% and 8% CO2 concentrations, and their responses were more profound during the 8% CO2 condition.
authors.affiliation: Department of Sport, Leisure, and Exercise Science, University of Connecticut, Storrs 06269-1110, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Maresh
authors.forename: L E
authors.initials: LE
authors.lastname: Armstrong
authors.forename: S A
authors.initials: SA
authors.lastname: Kavouras
authors.forename: G J
authors.initials: GJ
authors.lastname: Allen
authors.forename: D J
authors.initials: DJ
authors.lastname: Casa
authors.forename: M
authors.initials: M
authors.lastname: Whittlesey
authors.forename: K E
authors.initials: KE
authors.lastname: LaGasse
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001944:Breath Tests; D002245:Carbon Dioxide / Q000097:blood*; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology* / Q000523:psychology*; D008297:Male; D008889:Military Personnel; D016273:Occupational Exposure; D010465:Perception; D012119:Respiration; D012677:Sensation; D011795:Surveys and Questionnaires
chemical_list: D002245:Carbon Dioxide