35% Carbon dioxide and breath-holding challenge tests in panic disorder: a comparison with spontaneous panic attacks

Respiration and its control mechanisms may represent an important system involved in abnormal anxiety. Our aim was to compare the demographic and clinical features of patients with panic disorder (PD) with agoraphobia (DSM‐IV) who had a panic attack after both the 35% carbon dioxide (CO2) test and the breath‐holding test (CPA group), and compare them with PD patients who did not have a panic attack after both tests (NPA group). We examined 76 patients with PD who were administered a 35% CO2test and a breath‐holding test within a 1‐week interval. Anxiety scales were applied before and after each test. A panic attack was induced in 50 (65.8%) patients during the CO2test (χ2 = 28.44, df = 1, P