Effects of induced hyperventilation on electrodermal response habituation to agoraphobia-relevant stimuli

The role of hyperventilation in the aetiology of anxiety disorders was investigated in an analogue study. It was hypothesised that induced hyperventilation would alter subsequent subjective and physiological responses to visually presented agoraphobic material. Three groups (N = 16) of students were used and each was divided into two sub-groups which were presented with slides of either potentially agoraphobic or neutral content. During the first phase of the experiment, subjects were exposed to 10 slides whilst their breathing rate was manipulated. Group FB was instructed to hyperventilate by asking the subjects to breathe fast and deeply, Group SB was instructed to breathe at a slow rate and Group NB breathed normally. After a recovery phase, subjects were re-exposed to the same visual stimuli as used in the first phase of the experiment. Measures of skin conductance response amplitude were obtained for each stimulus in the series. In addition, heart rate and respiration were monitored, and subjective measures of somatic and affective states were obtained. Subjects also rated the pleasantness of the stimuli. The hyperventilation instructions resulted in delayed electrodermal habituation relative to the other groups. This finding could not be accounted for in terms of group differences in either physiological or subjective 'arousal'.