Respiratory Psychophysiology of Panic Disorder: Three Respiratory Challenges in 98 Subjects
It is now well established that CO2 inhalation causes more anxiety and panic in patients with panic disorder than in normal volunteers (1–9). CO2-induced panic resembles naturally occurring panic (10). CO2 hypersensitivity is not simply a manifestation of dyspnea induced by CO2 (11) and cannot be explained by baseline anxiety level differences between patients and comparison subjects (12). Panic patients exhibit hypersensitivity to CO2 even when their anxious response is comparable to that of normal comparison subjects (6). Heightened CO2 sensitivity in asymptomatic first- degree relatives of patients with panic disorder suggest that the response may be a trait phenomenon (13). While the enhanced sensitivity of panic disorder patients to inhaled CO2 has been unequivocally established, the nature of the specific respiratory abnormalities in panic disorder remains controversial.