Validation of Non-Invasive CO2 Tolerance Field Test

INTRODUCTION: Breathwork, or the specific act of controlling breathing to elicit a desired outcome, is not only a potential way to improve one’s mental well-being but also to alter adaptative responses through gas exchange at the capillary level. Increasing tolerance to carbon dioxide (CO2) has been positively correlated with improvement in athletic performance and reduction of stress and anxiety. However, there does not exist a validated non-invasive test to accurately measure one’s tolerance to CO2. PURPOSE: The purpose of this study was to validate the only currently known CO2 tolerance (CO2T) field test against measured maximal dissolved CO2 and maximal ventilatory carbon dioxide (V̇CO2max) in endurance athletes. HYPOTHESIS: It was hypothesized that the novel CO2T field test would have a strong positive correlation to clinical CO2 measurements, there would be no observable differences in comparative values between the CO2T field test and clinical CO2 measurements between sexes, and there would be a negative correlation between anaerobic capacity and CO2T. METHODS: Twenty-eight (n=28, 19 males, 9 females) participants reported to the Human Performance Laboratory on two separate occasions, separated by 48 hours, for testing. Peak CO2 levels were generated via repeated 30-second Wingate anaerobic power intervals with two minutes of rest in-between. Participants continued the Wingate tests until a plateau of peak power was achieved or volitional fatigue. CO2 data were recorded at the end of each interval. Day one consisted of a study orientation, informed consent, anthropometric measurements, CO2T field test, and ventilatory CO2 measurements during the repeated Wingate tests. Day two consisted of a second CO2T field test, end-tidal CO2 (EtCO2), and lactate (BL) measurements during the repeated Wingate tests. STATISTICS: Repeated measures ANOVA and paired t-test were used to determine if differences existed between CO2T times, EtCO2, anaerobic capacity (AC), and blood BL values. Pearson correlation coefficient analysis was used to determine if there was a relationship between CO2T times and all primary research variables. RESULTS: The CO2T field test showed to have a very high degree of intra-rater reliability but did not show any validity to CO2 measurements. Statistical analysis showed a high positive correlation between CO2T tests one and two (r = 0.989, p < 0.01) and no significant difference so an average score was used for analysis. A moderate positive correlation to HRpeak for CO2Tavg (r = 0.38, p < 0.05), and an indirect correlation to EtCO2(1) (r = -0.342, p < 0.05). Correlations between CO2T tests and all other variables did not reach statistical significance. CONCLUSION: While reliable, the novel CO2T field test does not seem to be a valid measurement of physiological levels of CO2. The test was shown to have a high degree of intra-rater reliability and could be used to show trends over time but does not give an accurate portrayal of actual CO2 production, accumulation, and tolerance.