Feedback of end-tidal pCO2 as a therapeutic approach for panic disorder - Meuret et al. (2008)

Key Points

  • Slow breathing with smaller volume can be achieved via CO2 feedback

  • Breathing training with CO2 feedback improves clinical outcomes in patients with panic disorder

  • After 1 year, 68% of patients had not experienced a panic attack since the training

The Breathing Diabetic Summary

This is a follow-on study to the Meuret et al. (2004) paper we recently reviewed.  In that one, we heard a somewhat anecdotal account of how CO2-feedback training can increase resting CO2, reduce breathing volume, and reduce/eliminate panic attacks.  Here, the authors present more data to support their breathing training protocol.

As a brief reminder, hyperventilation is a major component of panic disorder and breathing training generally leads to positive outcomes.  However, most studies focus on breathing slower, not less.  Carbon dioxide is rarely measured.  And, as we’ve seen before, people often overcompensate when breathing slowly.  Thus, they breathe slow, but they are still hyperventilating. 

The aim of this study was to teach patients with panic disorder to breathe slowly and breathe less, with the overall goal of reducing the risk of hyperventilation-induced panic attacks.

They studied 37 patients with panic disorder.  At the start of the study, 26 of them had low resting CO2 values (<35 mm Hg, which is considered hypocapnic), indicating that they were in a constant state of mild hyperventilation.  They assigned 20 patients into their breathing training group and the other 17 into a “wait list” to serve as a control group.

They taught the breathing group about the role of breathing in panic disorder and helped them to notice their own problematic breathing patterns.  Then, they hooked them up to a CO2 monitor so they could see how different breathing patterns affected CO2 levels.  Once hooked up, they also showed them different ways to lower breathing rate while simultaneously increasing CO2.  Finally, they were sent home with the CO2 device and instructed to practice 17 minutes of this breathing (low rate, high CO2) twice a day.  They had a tape of different tones to guide their breathing toward slower rates.  They started out at 13 breaths/min the first week, and then reduced to 11, 9, and finally 6 breaths/min in the final week of the treatment.

The results showed that patients were able to comply with the protocol fairly easily, with only 4 patients dropping out by the 1-year follow-up.  Looking at the short-term results, the patients in the breathing group significantly reduced breathing rate, increased CO2, and reduced psychophysiological symptoms of panic, whereas the wait list group did not change.  As the treatment progressed over time, CO2 levels increased to normal and breathing rate steadily declined.  Anxiety and panic attacks also decreased.

At the 1-year follow-up, patients were experiencing significantly less panic attacks.  In fact, 68% of them had not experienced a panic attack since the training.  One interesting result was that the patients without any obvious breathing problems at the start of the study improved to the same degree as those with breathing disorders.  Thus, there appears to be a psychological component to breathing exercises that helps with anxiety and panic.  In my opinion, it’s likely the feeling of control over one’s emotions that accompanies breathing practices.

The authors believe that the breathing exercises also made the patients more resilient to changes in CO2, which would reduce any feelings of suffocation and reduce hyperventilation.  Both of these would reduce risk of panic.

Overall, this study provides evidence that CO2 feedback can train patients to breathe slowly while also breathing less, allowing them to normalize CO2 levels. This leads to better physiological and mental resilience, and significantly less panic attacks. I believe CO2 feedback would be beneficial for many other disease states, and health in general, as taking “big breaths” is so commonly (and wrongly) advised. However, until CO2 devices are cheaper, my advice is to use Principle 1 to both reducing your breathing rate and breathing volume.

Abstract from Paper

BACKGROUND: Given growing evidence that respiratory dysregulation is a central feature of panic disorder (PD) interventions for panic that specifically target respiratory functions could prove clinically useful and scientifically informative. We tested the effectiveness of a new, brief, capnometry-assisted breathing therapy (BRT) on clinical and respiratory measures in PD.

METHODS: Thirty-seven participants with PD with or without agoraphobia were randomly assigned to BRT or to a delayed-treatment control group. Clinical status, respiration rate, and end-tidal pCO(2) were assessed at baseline, post-treatment, 2-month and 12-month follow-up. Respiratory measures were also assessed during homework exercises using a portable capnometer as a feedback device.

RESULTS: Significant improvements (in PD severity, agoraphobic avoidance, anxiety sensitivity, disability, and respiratory measures) were seen in treated, but not untreated patients, with moderate to large effect sizes. Improvements were maintained at follow-up. Treatment compliance was high for session attendance and homework exercises; dropouts were few.

CONCLUSIONS: The data provide preliminary evidence that raising end-tidal pCO(2) by means of capnometry feedback is therapeutically beneficial for panic patients. Replication and extension will be needed to verify this new treatment's efficacy and determine its mechanisms.

Journal Reference:

Meuret AE, Wilhelm FH, Ritz T, and Roth WT, (2008) Feedback of end-tidal pCO2 as a therapeutic approach for panic disorder, Journal of Psychiatric Research, 42(7), 560-568,