Researchers at Southern Methodist University (Dallas, TX, USA; www.smu.edu) developed the Capnometry-Assisted Respiratory Training (CART) biological-behavioral treatment program, which teaches patients to breathe in such a way as to reverse hyperventilation, a highly uncomfortable state where the blood stream operates with abnormally low levels of carbon dioxide (CO2). The goal of the exercises is to reduce chronic and acute hyperventilation and associated physical symptoms using a CO2 capnometer for biofeedback control, achieved by breathing slower but most importantly more shallowly; contrary to common belief, taking deep breaths actually worsens hyperventilation and symptoms.

To test the program, 41 patients with panic disorder and agoraphobia were randomly assigned to receive 4 weeks of training aimed at altering either CART or panic-related cognitive training. Changes in respiration (PCO2, respiration rate), symptom appraisal, and a modality-nonspecific mediator (perceived control) were considered as possible mediators. The researchers found that CART, but not cognitive training, led to corrections from initially hypocapnic to normocapnic levels. The reductions in panic symptom severity and panic-related cognitions, and the improvements in perceived control were significant and comparable in both treatment groups. The study was published in the October 2010 issue of the Journal of Consulting and Clinical Psychology.

"Most panic-disorder patients report they are terrified of physical symptoms such as shortness of breath or dizziness," said one of the researchers, psychologist and panic disorder expert Alicia Meuret, PhD. "In our study, cognitive therapy didn't change respiratory physiology, but CART did effectively reduce hyperventilation. CART was proved an effective and powerful treatment that reduces the panic by means of normalizing respiratory physiology."

There are numerous theories of panic disorder, each proposing a unique pathway of change leading to treatment success. However, little is known about whether the improvements in the proposed mediators are indeed associated with treatment outcomes, and whether these mediators are specific to particular treatment modalities.

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