Mt. Hegel et Rj. Ferguson, PSYCHOPHYSIOLOGICAL ASSESSMENT OF RESPIRATORY-FUNCTION IN PANIC DISORDER - EVIDENCE FOR A HYPERVENTILATION SUBTYPE, Psychosomatic medicine, 59(3), 1997, pp. 224-230
Objective: Previous research has found differences in respiratory func
tion between panic disorder and other anxiety disorder populations. Th
ese differences have been explained as reflecting either a) a specific
feature of panic disorder, b) merely a sign of increased general arou
sal, or c) a result of population sampling error. The current study ad
dressed the question of such differences by using improved methodology
over previous research. A preliminary evaluation of respiratory sympt
oms during panic attacks was undertaken as a means of identifying a re
spiratory-sensitive subtype of the panic patient. Method: Seventeen pa
nic disorder patients (PD), 18 patients with generalized anxiety disor
der (GAD), and 20 normal control (NC) subjects were administered a psy
chophysiological evaluation composed of baseline, stressor, and recove
ry phases. Panic patients were measured for the severity of respirator
y symptoms during panic attacks. End-tidal CO2 (EtCO2) and respiration
rate were measured throughout the psychophysiological evaluation. Res
ults: PDs demonstrated significantly lower baseline EtCO2 levels than
the GADs and NCs, in spite of being equivalent to GADs on baseline anx
iety levels. Moreover, panic patients reporting a high level of respir
atory symptoms during panic attacks seemed to account for the bulk of
observed differences. Conclusions: These findings lend support to a gr
oup of studies showing differences in respiratory function between pan
ic disorder and other anxiety disorder populations. In addition, this
study provides preliminary support for the presence of a distinct ''hy
perventilation subtype'' of panic disorder. The implications of these
findings for future research and treatment are discussed.