Abstract
Our aim was to describe the clinical features of 35% CO 2-induced panic attacks in patients with panic disorder (PD) ( Diagnostic and Statistical Manual and Mental Disorders, Fourth Edition) and compare them with the last spontaneous panic attack in patients with PD who had not had a panic attack after the 35% CO 2 challenge test. We examined 91 patients with PD submitted to the CO 2 challenge test. The test consisted of exhaling as fully as possible, took a fast vital capacity breath, held their breath for 8 seconds, exhaled, and then repeated the fast vital capacity breath, again holding for 8 seconds. The patients inhaled the 35% CO 2/65% O 2 mixture or atmospheric compressed air, randomly selected in a double-blind design. Scales were applied before and after the test. A total of 68.1% (n = 62) patients with PD had a panic attack (responders) after the CO 2 test ( χ 2 1 = 25.87, P = .031). The last spontaneous panic attack and the symptom profile from the patients with PD who had not had a panic attack after the test (n = 29, 31.9%) were described to compare. The responders had more respiratory symptoms ( χ 2 1 = 19.21, P < .001), fulfilling the criteria for respiratory PD subtype (80.6%); the disorder started earlier (Mann-Whitney, P < .001), had a higher familial prevalence of PD ( χ 2 1 = 20.45, P = .028), and had more previous depressive episodes ( χ 2 1 = 27.98, P < .001). Our data suggest that there is an association between respiratory PD subtype and hyperreactivity to a CO 2 respiratory challenge test. The responders may be a subgroup of respiratory PD subtype with future diagnostic and therapeutic implications.
Published Version
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