Suffocation and respiratory responses to carbon dioxide and breath holding challenges in individuals with panic disorder

Objective: Findings showing that individuals with panic disorder (PD) are prone to experience panic attacks when inhaling CO₂-enriched air have given rise to the hypothesis that physiological systems underlying the experience of suffocation may be important in the etiology of PD. In this study, we tested several predictions stemming from this view. Methods: Forty individuals with PD and 32 controls underwent both a breath-holding challenge and a CO₂ rebreathing challenge. A wide array of physiological and psychological responses, including continuous measurements of subjective suffocation, was recorded. Results: Individuals with PD experienced elevated physiological reactivity to both challenges and greater levels of suffocation sensations during the rebreathing challenge. Furthermore, PD individuals who experienced a panic attack in response to the rebreathing challenge exhibited faster but shallower breathing during the challenge than did other PD individuals. Conclusion: Findings are consistent with theories linking PD to hypersensitive brain systems underlying the experience of suffocation. The possibility that subjective suffocation was in part mediated by peripheral interoceptive disturbances (vs. brainstem dysregulation) is discussed.