Characteristics of sighing in panic disorder

Background: Sighs, breaths wit larger tidal volumes than surrounding breath s, have been reported as being more frequent in patients with anxiety disor ders. Methods: Sixteen patients wit panic disorder, 15 with generalized anxiety d isorder, and 19 normal control subjects were asked to sit quietly for 30 mi n. Respiratory volumes and timing were recorded wit inductive plethysmograp hy and expired pCO(2), from nasal prongs. Results: Panic disorder patients sighed more and had tonically lower end-ti dal pCO(2) than control subjects, whereas generalized anxiety disorder pati ents were intermediate. sighs defined as >2.0 times the subject mean discri minated groups best. Sigh frequency was more predictive of individual pCO(2 ) levels than was minute volume. Ensemble averaging of respiratory variable s for sequences of breaths surrounding sighs showed no evidence that sighs were triggered by increased pCO(2) or reduced tidal volume in any group. si gh breaths were larger in panic disorder patients than in control subjects. After sighs, pCO(2) and tidal volume did not return to baseline levels as quickly in panic disorder patients as in control subjects. Conclusions: Hypocapnia in panic disorder patient sin related to sigh frequ ency. In none of the groups was sighing a homeostatic response. panic disor der patients show less peripheral chemoreflex gain than control subjects, w hich would maintain low pCO(2) levels after sighing. Biol Psychiatry 2001;4 9:606-614 (C) 2001 Society of Biological Psychiatry.