, 2008; Zvolensky & Eifert, 2001). This CO2 concentration has been used successfully in past work to elicit anxious and fearful responding to bodily sensations (Bernstein, Zvolensky, Marshall, & Schmidt, 2009), although it is not fully clear what mechanisms contribute to such effects (Abrams et al.). The third phase consisted of a 5-min postchallenge recovery period. selleck Participants completed anxiety ratings throughout the procedure as instructed by an audio recording (for a full summary of the challenge procedure, please see Vujanovic & Zvolensky, 2009). Two participants removed their masks and requested discontinuation of the CO2-enriched air administration at Minutes 3.03 and 3.35 of the 4-min challenge procedure, respectively. Both participants completed all remaining self-report questionnaires and physiological monitoring.
Results Manipulation Checks and Descriptive Characteristics Please see Table 1 for descriptive data and group differences in prechallenge (Minute 9 of prechallenge baseline) and postchallenge (Minute 4 of challenge, immediately after termination of CO2 administration) anxiety measures. Within the total sample, heart rate, t(57) = 6.94, p < .001, and skin conductance level, t(57) = 5.99, p < .001, significantly increased from prechallenge to postchallenge. Respiration rate, t(31) = 1.82, p = .08, and SUDS ratings, t(61) = 1.88, p = .07, did not significantly increase from prechallenge to postchallenge, although a trend toward formal levels of statistical significance emerged for both variables.
When examining the cigarette deprivation and smoking-as-usual groups separately, the pattern remained the same with the exception that the smoking-as-usual group evidenced a significant increase in SUDS ratings from prechallenge to postchallenge, t(34) = 3.37, p < .01. Table 1. Carbon dioxide�CEnriched Air Laboratory Challenge Manipulation Checks: Prechallenge to Postchallenge Comparisons on Self-report Anxiety Ratings and Physiological Responding Tests of between-group differences were conducted to identify covariates that might correct for any potential failures of randomization indicated by significant group differences. Significant differences between groups were found in terms of age, CO analysis of breath sample readings (prechallenge), and nicotine withdrawal symptoms (prechallenge). No gender differences were noted with regard to any of the studied variables.
The smoking-as-usual group was significantly Brefeldin_A older than the cigarette deprivation group (M = 34.1, SD = 13.9 and M = 26.3, SD = 10.5; t(61) = ?2.41, p < .05). Therefore, age was entered as a covariate in each of the models to correct for failure of randomization. As expected, upon arrival to the laboratory for the challenge session, the cigarette deprivation group endorsed significantly higher levels of nicotine withdrawal symptoms than the smoking-as-usual group (M = 8.2, SD = 4.6 and M = 4.4, SD = 5.1; t(61) = 2.99, p = .