Relationships between the anxiety sensitivity index, the suffocation fear scale, and responses to CO₂ inhalation

Interest in documenting ways to predict anxious responding in panic disorder (PD) patients has proliferated recently in the literature. In the current study, two self-report measures were assessed to determine their relative utility in predicting responses to a panicogenic challenge. The Anxiety Sensitivity Index (ASI) and the Suffocation Fear Scale (SFS) were evaluated by correlating scores on these measures with reactions to inhalation of 35% carbon dioxide (CO₂), assessed via anxiety ratings, panic symptom intensity, tidal volume (V_T) and respiratory rate (RR). A sample of 14 PD patients and 14 matched control (MC) participants demonstrated that the relationship between ASI scores and responses to 35% CO₂ were stronger than the relationship between SFS scores and responses to CO₂. Specifically, both respiratory responses (V_T and RR) and self-reported reactions (anxiety and symptom intensity) were significantly correlated with scores on the ASI. In contrast, scores on the SFS were significantly correlated with only one measure of respiratory change (V_T). Although preliminary, these data indicate that the ASI may be a more useful tool than the SFS in predicting self-reported and respiratory responses to CO₂ challenges.