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Imagined Risk of Suffocation as a Trigger for Hyperventilation

From the Department of Psychology, University of Leuven, Leuven, Belgium (I.V.D., S.D.P., S.D., E.W., O.V.d.B.); Faculty of Medicine, University of Leuven, Leuven, Belgium (P.V.d.W.).

Address correspondence and reprint requests to Ilse Van Diest, PhD, University of Florida, CSEA, 2800 SW. Archer Rd., Surge Bldg. 772, Gainesville, FL 32608. E-mail: Ilse.Vandiest{at}psy.kuleuven.ac.be

Objective: Although hyperventilation has been hypothesized to play a role in many pathologies, its critical triggers remain poorly understood. The present experiment aimed to test whether stronger hyperventilation responses occur in response to suggested risk of suffocation compared with other fearful situations in high- and low-trait anxious women.

Methods: Fractional end-tidal CO₂-concentration (FetCO₂), respiratory frequency, and inspiratory volume were measured nonintrusively in high- (n = 24) and low- (n = 24) trait anxious women during imagery of 3 fear, 1 tension, 1 depressive, and 3 relaxation scripts. The fear scripts were equal in ratings of unpleasantness and arousal but differed regarding the inclusion of suggested risk of suffocation and entrapment. After each imagery trial, participants rated the emotional dimensions of pleasantness, arousal, and dominance and the vividness of their imagery.

Results: Decreases in FetCO₂ occurred in all fear scripts. High-trait anxious women showed a stronger reduction in FetCO₂ compared with low-trait anxious women during the fear script suggesting risk of suffocation but not during the other fear scripts. This effect was unrelated to any of the self-reported fear ratings. Self-reported fear of entrapment was associated with an overall lower FetCO₂ but not with enhanced reactivity to imagined entrapment.

Conclusion: High-trait anxiety is associated with stronger respiratory responsivity to imagined risk of suffocation and may constitute a specific vulnerability factor for the development of panic disorder and claustrophobia.

Key Words: hyperventilation • trait anxiety • suffocation • fear • entrapment

Abbreviations: FetCO₂ = fractional concentration of end-tidal carbon dioxide; f_r = respiratory frequency; Vi = inspiratory volume; CPS = checklist for psychosomatic symptoms; STAI-T = trait version of the state-trait anxiety inventory; FS = fear of suffocation; FR = fear of restriction.