RESPIRATORY PSYCHOPHYSIOLOGY OF PANIC DISORDER - 3 RESPIRATORY CHALLENGES IN 98 SUBJECTS

Objective: Respiratory abnormalities may play a central role in the pa thophysiology of panic disorder. The current study was undertaken to e xamine the respiratory response in the largest series of subjects to d ate during three respiratory challenges that used improved methodology . Method: Fifty-nine patients with DSM-III-R panic disorder and 39 nor mal volunteers were challenged with 5% and 7% CO2 inhalation and room air hyperventilation separated by room nir breathing with continuous s pirometry. Results: Patients with panic disorder were more sensitive t o the anxiogenic effects of CO2 than were normal subjects, and CO2 was a more potent stimulus to panic than hyperventilation. Patients incre ased their respiratory rate more quickly during CO2 inhalation than di d comparison subjects, and this increase preceded the panic attacks. P atients who panicked in response to 5% CO2 demonstrated continued rise in end-tidal CO2, while the end-tidal CO2 of the comparison groups st abilized. Low end-tidal CO2 and high variance in minute ventilation at baseline predicted panic attacks during CO2 inhalation. Following CO2 or hyperventilation challenges, respiratory rate dropped sharply, whi le tidal volume remained elevated longer in patients than in compariso n subjects. Conclusions: The findings confirm the greater behavioral a nd physiological sensitivity of patients with panic disorder CO2 inhal ation and identify a series of respiratory abnormalities. Panic attack s in panic disorder may be examined by inefficient compensatory mechan isms, primarily of respiratory rate.