Physiological and symptom responses to hyperventilation: A comparison of frequent and infrequent panickers

Ten subjects with panic disorder and ten subjects with infrequent panic attacks were assessed during 2 min of voluntary hyperventilation using four measures of physiological arousal (heart rate, upper trapezious EMG, skin conductance, and digital skin temperature). Immediately following hyperventilation, subjects were asked to rate their degree of distress on 13 panic symptoms, derived from DSM-III criteria for panic disorder. Results indicated that frequent panickers had significant overall elevations in trapezious EMG, relative to infrequent panickers, and demonstrated a slight increase in muscle tension following hyperventilation. In contrast, infrequent panickers showed a trend toward greater vasodilation preceding and during hyperventilation, with subsequent vasoconstriction upon resumption of normal breathing. Increases in skin conductance and heart rate were noted for both samples during hyperventilation, as reported in prior research. Symptom distress ratings indicated that the infrequent panickers reported significantly greater distress from dizziness and trembling in response to overbreathing, contrary to prediction. Implications of these findings are discussed in light of current accounts of cognitive and physiological factors in the etiology of panic attacks and panic disorder.This research was supported by Biomedical Research Support Grant #507RR07147, National Institutes of Health.