Chest
Volume 127, Issue 5, May 2005, Pages 1808-1811
Journal home page for Chest

Opinions/Hypotheses
Hypocapnia and Asthma: A Mechanism for Breathing Retraining?

https://doi.org/10.1378/chest.127.5.1808Get rights and content

There is some evidence that breathing retraining may be beneficial for patients with asthma, but the mechanism behind this benefit is still unknown. One hypothesis is that individuals can be trained to raise carbon dioxide levels and thereby reverse the bronchoconstrictive effects of hypocapnia and utilize the bronchodilatory effects of hypercapnia. This theory presupposes that individuals with asthma have lower carbon dioxide levels than the healthy population. This article reviews the available evidence supporting the hypothesis and concludes that although attractive, there is currently insufficient evidence to attribute the benefits of breathing retraining to this mechanism.

Section snippets

Search Strategy

Multiple strategies were incorporated to maximize identification of suitable studies. We searched MEDLINE, EMBASE, Cochrane library, CINAHL, and reference lists of original and review articles. Authors of relevant abstracts were contacted to seek additional information.

Hypocapnia

The Paco2 reflects the balance between the production and elimination of carbon dioxide. Under normal conditions, the Paco2 is maintained at approximately 39 to 41 mm Hg by alveolar ventilation under the control of respiratory centers in the pons and medulla.5 Changes in the production of carbon dioxide are usually accompanied by corresponding alterations in alveolar ventilation with little or no change in Paco2. The main physiologic causes for hypocapnia are related to hyperventilation. Mild

Hypocapnia and Bronchoconstriction

Although hypocapnia is a consistent finding in acute asthma, it is not certain whether it has any clinically relevant pathogenic role. Proponents of the Buteyko breathing technique7 would suggest that this is the case. Also, in 1968 it was hypothesized in the New England Journal of Medicine8 that hypocapnia during an asthma attack could perpetuate bronchospasm and lead to a cycle of progressive hypocapnia and increasing bronchospasm. There is a body of experimental evidence that supports this

Hypocapnia and Asthma

In 1952, Buteyko theorized that “hidden” hyperventilation is the basic cause of asthma,7 linked to the inflammatory and structural changes characteristic of the disease. During acute episodes of asthma, hyperventilation leading to hypocapnia is well documented,62425 but very few studies192627 have suggested that patients with asthma are hypocapnic when their asthma is stable. In 1988, Hormbrey et al27 compared carbon dioxide response and breathing pattern in patients with asthma, patients with

Future Research

Although breathing control and breathing training are common interventions for respiratory conditions, there is a paucity of randomized clinical trials examining their effectiveness or the mechanism for any effect. A recent Cochrane review stated that “no reliable conclusions can currently be drawn concerning the use of breathing exercises for asthma in clinical practice.”35 However, trends for improvement are encouraging; further large-scale trials, including full descriptions of treatment

Conclusion

There is now some evidence that asthmatic individuals have lower levels of carbon dioxide than the healthy population, even when they are stable and asymptomatic. There is also some indirect evidence that a significant proportion of the stable asthmatic population have symptoms of hyperventilation. Physiotherapists and others regularly use breathing retraining techniques to alleviate these symptoms, with some reported benefits. While these may be related to raising an individual's carbon

References (35)

  • GluckSL

    Acid-base

    Lancet

    (1998)
  • RitzT et al.

    The structure of symptom report in asthma: a reevaluation

    J Psychosom Res

    (2001)
  • BraganzaS et al.

    The use of complementary therapies in inner-city asthmatic children

    J Asthma

    (2003)
  • ThomasM et al.

    Breathing retraining for dysfunctional breathing in asthma: a randomized controlled trial

    Thorax

    (2003)
  • ManochaR et al.

    Sahaja yoga in the management of moderate to severe asthma: a randomized controlled trial

    Thorax

    (2002)
  • CooperS et al.

    Effect of two breathing exercises (Buteyko and pranayama) in asthma: a randomized controlled trial

    Thorax

    (2003)
  • LaffeyJG et al.

    Hypocapnia

    N Engl J Med

    (2002)
  • StalmatskiA

    Freedom from asthma: Buteyko's revolutionary treatment

    (1997)
  • Hypoxemia and hypocapnia in asthma [abstract]

    N Engl J Med

    (1968)
  • ReynoldsAM et al.

    Tachykinins mediate hypocapnia-induced bronchoconstriction in guinea pigs

    J Appl Physiol

    (1989)
  • D'AngeloE et al.

    The effects of CO2on respiratory mechanics in anesthetized paralyzed humans

    Anesthesiology

    (2001)
  • IngramRH

    Effects of airway versus arterial CO2changes on lung mechanics in dogs

    J Appl Physiol

    (1975)
  • KolbeJ et al.

    Hypocapnia-induced constriction of the canine peripheral airways exhibits tachyphylaxis

    J Appl Physiol

    (1987)
  • LindemanKS et al.

    Hypocapnia-induced contraction of porcine airway smooth muscle

    Eur Respir J

    (1998)
  • SterlingGM

    The mechanism of bronchoconstriction due to hypocapnia in man

    Clin Sci

    (1968)
  • NewhouseMT et al.

    Effect of alterations in end-tidal CO2tension on flow resistance

    J Appl Physiol

    (1964)
  • NielsenTM et al.

    The effect of CO2on peripheral airways

    Acta Physiol Scand

    (1976)
  • Cited by (37)

    • Controlling Asthma by Training of Capnometry-Assisted Hypoventilation (CATCH) vs slow breathing: A randomized controlled trial

      2014, Chest
      Citation Excerpt :

      The reported effects are clinically important and show promise in addressing an unmet need in a population where overall level of control remains unsatisfactory. Hypoventilation training for asthma has been advocated for some time,2,12,32but despite the centrality of elevating Pco2in its therapeutic rationale, no prior study has targeted Pco2levels directly, except for our pilot study.17 In the present study, we instituted the most rigorous test possible for Pco2as the active ingredient in that the comparison group followed the same prescriptions of slow breathing and feedback of RR as CART but was not provided with shallow breathing instructions or feedback of Pco2.

    • Buteyko breathing method

      2013, Recognizing and Treating Breathing Disorders: A Multidisciplinary Approach
    View all citing articles on Scopus

    Dr. Bruton is funded by a Postdoctoral Research Fellowship from the UK Department of Health.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestjournal.org/misc/reprints.shtml).

    View full text