Carbon dioxide inhalation challenges in idiopathic environmental intolerance

Background: Idiopathic environmental intolerance (IEI) is associated with u nexplained physical symptoms, which overlap considerably with those of pani c disorder (PD), Objective: This study tested the hypothesis that patients with symptoms to suggest IEI exhibit features of PD in response to nonnoxious environmental stimuli. Methods: A single-blind, case-control 35% carbon dioxide inhalation challen ge was conducted at a university-based occupational health unit with the us e of standardized psychologic questionnaires involving 36 patients with IEI and 37 healthy control subjects. The main outcome measures included panic attack symptoms and scores on the Anxiety Sensitivity Index, a measure of p anic-related anxiety. Results: Patients with IEI scored significantly higher on the Anxiety Sensi tivity Index than control subjects did (P < .05). Significantly more patien ts with IEI (71%) than control subjects (26%) fulfilled panic attack criter ia after carbon dioxide (P < .001). Physiologic responses to the challenge were not significantly different between groups. Conclusions: Results suggest that, similar to patients with PD, patients wi th DEI display high anxiety sensitivity and in response to carbon dioxide i nhalation tend to experience heightened anxiety and panic attacks.