Biofeedback Training to Increase PCO2 in Asthma with Elevated Anxiety: A One-Stop Treatment for Both Conditions?

OBJECTIVE: Anxiety is highly prevalent in individuals with asthma. Asthma symptoms and medication can exacerbate anxiety, and vice versa. Unfortunately, treatments for comorbid anxiety and asthma are largely lacking. A problematic feature common to both conditions is hyperventilation. It adversely affects lung function and symptoms in asthma and anxiety. We examined whether a treatment to reduce hyperventilation, shown to improve asthma symptoms, also improves anxiety in asthma patients with high anxiety.

METHOD: One-hundred-twenty English- or Spanish-speaking adult patients with asthma were randomly assigned to either capnometry-assisted respiratory training (CART) to raise PCO2 or feedback to slow respiratory rate (SLOW). Although anxiety was not an inclusion criterion, 21.7% met clinically-relevant anxiety levels on the Hospital Anxiety and Depression scale. Anxiety (HADS-A) and depression (HADS-D) scales, anxiety sensitivity (ASI), and negative affect (PANAS-N) were assessed at baseline, posttreatment,1-month follow-up, and 6-month follow-up.

RESULTS: In this secondary analysis, asthma patients with high baseline anxiety showed greater reductions in ASI and PANAS-N in CART than in SLOW (ps ≤ .005, Cohen's ds ≥ .58). Further, at 6-month follow-up, these patients also had lower ASI, PANAS-N, and HADS-D in CART than in SLOW (ps ≤ .012, Cohen's ds ≥ .54). Patients with low baseline anxiety did not have differential outcomes in CART than in SLOW.

CONCLUSIONS: For asthma patients with high anxiety, our brief training designed to raise PCO2 resulted in significant and sustained reductions in anxiety sensitivity and negative affect compared to slow-breathing training. The findings lend support for PCO2 as a potential physiological target for anxiety reduction in asthma.Trial Registration:clinicaltrials.gov Identifier: NCT00975273.