Temporal stability of multiple response systems to 7.5% carbon dioxide challenge

- Self-rated anxiety and panic symptoms were most stable during CO2 breathing.
- Physiology was most stable during respiratory stimulation via 7.5% CO2.
- Physical versus cognitive symptoms showed higher stability during CO2 breathing.
- Escape/avoidance behaviors and panic attacks demonstrated poor reliability.
- Strong effect size estimates were observed for 7.5% CO2 breathing.

Self-reported anxiety, and potentially physiological response, to maintained inhalation of carbon dioxide (CO2) enriched air shows promise as a putative marker of panic reactivity and vulnerability. Temporal stability of response systems during low-dose, steady-state CO2 breathing challenge is lacking. Outcomes on multiple levels were measured two times, one week apart, in 93 individuals. Stability was highest during the CO2 breathing phase compared to pre-CO2 and recovery phases, with anxiety ratings, respiratory rate, skin conductance level, and heart rate demonstrating good to excellent temporal stability (ICCs ≥ 0.71). Cognitive symptoms tied to panic were somewhat less stable (ICC = 0.58) than physical symptoms (ICC = 0.74) during CO2 breathing. Escape/avoidance behaviors and DSM-5 panic attacks were not stable. Large effect sizes between task phases also were observed. Overall, results suggest good-excellent levels of temporal stability for multiple outcomes during respiratory stimulation via 7.5% CO2.