When dyspnea gets worse: Suffocation fear and the dynamics of defensive respiratory responses to increasing interoceptive threat.

In patients with anxiety and/or respiratory diseases, body sensations, particularly from the respiratory system, may increase in intensity and aversiveness and thus lead into defensive action (e.g., escape) or panic. The processes, however, that might contribute to the culmination of symptoms and the switch into defensive action have not been well understood yet. The current study aimed at evaluating an experimental paradigm to characterize the dynamics of defensive mobilization to body sensations increasing in intensity and aversiveness. Persons reporting low and high suffocation fear (SF; N = 69) were exposed to increasingly unpleasant feelings of dyspnea induced by inspiratory resistive loads and a breathing occlusion requiring voluntary breath holding. Respiratory responses were assessed along with subjective reports of anxiety and panic symptoms. Presentation of respiratory loads with increasing physical resistance led to increasingly unpleasant feelings of dyspnea. Twenty-eight participants terminated the exposure prematurely at least once. When dyspnea was severe, high compared to low SF persons exhibited an increased respiratory rate that was accompanied by reports of more intense panic symptoms. Premature terminations of exposure were preceded by a surge in anxiety, breathing frequency, and mouth pressure, and a decrease in tidal volume. We successfully established an experimental paradigm to assess changes in defensive responding with increasing intensity of an interoceptive threat. The current data foster our understanding of behavioral expression patterns observed in patients with anxiety and/or respiratory diseases and the processes involved in the culmination of bodily sensations and anxiety into panic.