PSYCHOPHYSIOLOGICAL ASSESSMENT OF RESPIRATORY-FUNCTION IN PANIC DISORDER - EVIDENCE FOR A HYPERVENTILATION SUBTYPE

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.