Respiratory Muscle Tension as Symptom Generator in Individuals With High Anxiety Sensitivity

Objective: Anxiety and panic are associated with the experience of a range of bodily symptoms, in particular unpleasant breathing sensations (dyspnea). Respiratory theories of panic disorder have focused on disturbances in blood gas regulation, but respiratory muscle tension as a source of dyspnea has not been considered. We therefore examined the potential of intercostal muscle tension to elicit dyspnea in individuals with high anxiety sensitivity, a risk factor for developing panic disorder. Methods: Individuals high and low in anxiety sensitivity (total N = 62) completed four tasks: electromyogram biofeedback for tensing intercostal muscle, electromyogram biofeedback for tensing leg muscles, paced breathing at three different speeds, and a fine motor task. Global dyspnea, individual respiratory sensations, nonrespiratory sensations, and discomfort were assessed after each task, whereas respiratory pattern (respiratory inductance plethysmography) and end-tidal carbon dioxide (capnography) were measured continuously. Results: In individuals with high compared to low anxiety sensitivity, intercostal muscle tension elicited a particularly strong report of obstruction (M = 5.1, SD = 3.6 versus M = 2.5, SD = 3.0), air hunger (M = 1.9, SD = 2.1 versus M = 0.4, SD = 0.8), hyperventilation symptoms (M = 0.6, SD = 0.6 versus M = 0.1, SD = 0.1), and discomfort (M = 5.1, SD = 3.2 versus M = 2.2, SD = 2.1) (all p values < .05). This effect was not explained by site-unspecific muscle tension, voluntary manipulation of respiration, or sustained task-related attention. Nonrespiratory control sensations were not significantly affe< 1), and respiratory variables did not reflect any specific responding of high-Anxiety Sensitivity Index participants to intercostal muscle tension. Conclusions: Respiratory muscle tension may contribute to the respiratory sensations experienced by panic-prone individuals. Theories and treatments for panic disorder should consider this potential source of symptoms.