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Original Research

Opposing Breathing Therapies for Panic Disorder: A Randomized Controlled Trial of Lowering vs Raising End-Tidal Pco2

Sunyoung Kim, PhD; Eileen Wollburg, PhD; and Walton T. Roth, MD

Published: July 15, 2012

Article Abstract

Background: Teaching anxious clients to stop hyperventilating is a popular therapeutic intervention for panic. However, evidence for the theory behind this approach is tenuous, and this theory is contradicted by an opposing theory of panic, the false-suffocation alarm theory, which can be interpreted to imply that the opposite would be helpful.

Objective: To test these opposing approaches by investigating whether either, both, or neither of the 2 breathing therapies is effective in treating patients with panic disorder.

Method: We randomly assigned 74 consecutive patients with DSM-IV-diagnosed panic disorder (mean age at onset = 33.0 years) to 1 of 3 groups in the setting of an academic research clinic. One group was trained to raise its end-tidal Pco2 (partial pressure of carbon dioxide, mm Hg) to counteract hyperventilation by using feedback from a hand-held capnometer, a second group was trained to lower its end-tidal Pco2 in the same way, and a third group received 1 of these treatments after a delay (wait-list). We assessed patients physiologically and psychologically before treatment began and at 1 and 6 months after treatment. The study was conducted from September 2005 through November 2009.

Results: Using the Panic Disorder Severity Scale as a primary outcome measure, we found that both breathing training methods effectively reduced the severity of panic disorder 1 month after treatment and that treatment effects were maintained at 6-month follow-up (effect sizes at 1-month follow-up were 1.34 for the raise-CO2 group and 1.53 for the lower-CO2 group; P < .01). Physiologic measurements of respiration at follow-up showed that patients had learned to alter their Pco2 levels and respiration rates as they had been taught in therapy.

Conclusions: Clinical improvement must have depended on elements common to both breathing therapies rather than on the effect of the therapies themselves on CO2 levels. These elements may have been changed beliefs and expectancies, exposure to ominous bodily sensations, and attention to regular and slow breathing.

Trial Registration: identifier: NCT00183521


J Clin Psychiatry 2012;73(7):931-939

Submitted: April 13, 2011; accepted January 27, 2012 (doi:10.4088/JCP.11m07068).

Corresponding author: Sunyoung Kim, PhD, Department of Psychology, University of Hawaii, Hilo, HI 96720 (


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Volume: 73

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