The practical use of carbon dioxide-induced anxiety in the diagnosis and care of patients with panic disorder.

The authors utilized inhalation of 35% carbon dioxide and 65% oxygen as a diagnostic tool in the evaluation of suspected panic disorder. In two inpatients admitted for a medical evaluation for pheochromocytoma and carcinoid syndrome, respectively, a positive response to the double-blind administration of CO2/O2 or room air was consistent with a diagnosis of panic disorder by psychiatric history. In two additional patients in whom denial of mental illness was a psychological impediment to proper treatment, a positive CO2/O2 challenge resulted in therapeutic benefit.