The Use of a Timed Exhale CO2 Tolerance Test as an Index of State/Trait Anxiety in Healthy Adults

Research supports the connection between breathing manipulation and emotional states, yet there is no established standard of quantification. This preliminary study investigates the validity and efficacy of a simple, practical test of tolerance to endogenous carbon dioxide tolerance as an index of anxiety. A sample of 41 nonclinical participants (24 males, 17 females) performed three trials of a CO2 tolerance test (CO2 TT)— a maximal duration exhale from vital capacity—on two separate days.

The CO2 TT out-performed a breath-hold test as an index of state anxiety. The findings of this study suggest that CO2 tolerance (CO2 T), as measured by a maximal duration exhale from vital capacity, serves as an index for state, and to a lesser degree, trait anxiety. With additional future research, CO2 T could become an important and easily accessible tool in assessing levels of and changes in anxiety.