Psychopathological description of hyperventilation-induced panic attacks: a comparison with spontaneous panic attacks.

Our aim was to describe the clinical features of hyperventilation-induced panic attacks (HPA) in panic disorder patients - DSM-IV - and to compare them with their spontaneous panic attacks and with spontaneous panic attacks in panic disorder (PD) patients not sensible to the hyperventilation challenge test. We reexamined 88 previously studied PD patients when they were submitted to a hyperventilation challenge test. They were induced to hyperventilate (30 breaths/min) for 4 min and anxiety scales were applied before and after the test. A total of 51.1% (n = 45) PD patients had a panic attack after hyperventilating - HPA (chi(2) = 13.11, d.f. = 1, p = 0.017). The clinical symptoms of the most severe panic attack were recorded by the HPA patient and by the PD patients not sensible to this test (non-HPA; n = 43, 48.9%) in a diary during a 1-week period and then compared. The HPA group had more respiratory symptoms (chi(2) = 15.26, d.f. = 1, p < 0.001), fulfilling the criteria for the respiratory PD subtype (75.6%), the disorder started later (Mann-Whitney, p < 0.001), had a higher familial prevalence of PD (chi(2) = 19.45, d.f. = 1, p = 0.036), and had more previous depressive episodes (chi(2) = 18.74, d.f. = 1, p < 0.001). The HPA group had similar symptomatology in spontaneous attacks and HPA. The HPA group may be regarded as a subgroup of the respiratory panic disorder subtype with diagnostic and therapeutic implications.