Clinical features of panic patients sensitive to hyperventilation or breath-holding methods for inducing panic attacks

our aim was to compare the clinical features of panic disorder (pd) patients sensitive to hyperventilation or breath-holding methods of inducing panic attacks. eighty-five pd patients were submitted to both a hyperventilation challenge test and a breath-holding test. they were asked to hyperventilate (30 breaths/min) for 4 min and a week later to hold their breath for as long as possible, four times with a 2-min interval. anxiety scales were applied before and after the tests. we selected the patients who responded with a panic attack to just one of the tests, i.e., those who had a panic attack after hyperventilating (hpa, n = 24, 16 females, 8 males, mean age ± sd = 38.5 ± 12.7 years) and those who had a panic attack after breath holding (bhpa, n = 20, 11 females, 9 males, mean age ± sd = 42.1 ± 10.6 years). both groups had similar (c2 = 1.28, d.f. = 1, p = 0.672) respiratory symptoms (fear of dying, chest/pain disconfort, shortness of breath, paresthesias, and feelings of choking) during a panic attack. the criteria of briggs et al. [british journal of psychiatry, 1993; 163: 201-209] for respiratory pd subtype were fulfilled by 18 (75.0%) hpa patients and by 14 (70.0%) bhpa patients. the hpa group had a later onset of the disease compared to bhpa patients (37.9 ± 11.0 vs 21.3 ± 12.9 years old, mann-whitney, p < 0.001), and had a higher family prevalence of pd (70.8 vs 25.0%, c2 = 19.65, d.f. = 1, p = 0.041). our data suggest that these two groups - hpa and bhpa patients - may be specific subtypes of pd.