Skip to main content

Main menu

  • Home
  • Current issue
  • ERJ Early View
  • Past issues
  • Authors/reviewers
    • Instructions for authors
    • Submit a manuscript
    • Open access
    • COVID-19 submission information
    • Peer reviewer login
  • Alerts
  • Podcasts
  • Subscriptions
  • ERS Publications
    • European Respiratory Journal
    • ERJ Open Research
    • European Respiratory Review
    • Breathe
    • ERS Books
    • ERS publications home

User menu

  • Log in
  • Subscribe
  • Contact Us
  • My Cart
  • Log out

Search

  • Advanced search
  • ERS Publications
    • European Respiratory Journal
    • ERJ Open Research
    • European Respiratory Review
    • Breathe
    • ERS Books
    • ERS publications home

Login

European Respiratory Society

Advanced Search

  • Home
  • Current issue
  • ERJ Early View
  • Past issues
  • Authors/reviewers
    • Instructions for authors
    • Submit a manuscript
    • Open access
    • COVID-19 submission information
    • Peer reviewer login
  • Alerts
  • Podcasts
  • Subscriptions

The case against inspiratory muscle training in COPD

M.I. Polkey, J. Moxham, M. Green
European Respiratory Journal 2011 37: 236-237; DOI: 10.1183/09031936.00095510
M.I. Polkey
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • For correspondence: m.polkey@rbht.nhs.uk
J. Moxham
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
M. Green
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Info & Metrics
  • PDF
Loading

Despite maximal medical therapy, many chronic obstructive pulmonary disease (COPD) patients remain breathless and this has led to persistent and commendable efforts to reduce symptoms and improve exercise performance using nonpharmacological approaches; some of these, for example pulmonary rehabilitation (PR) 1, comprising general exercise and fitness training, are of proven benefit, while others remain controversial.

Inspiratory muscle training (IMT), being cheap and free of side-effects, is intuitively attractive, since improving the capacity of the inspiratory muscles should “make breathing easier” and so improve exercise performance. Enthusiasts do not allow the superficial attractiveness of this proposition to be clouded by aspects of the data. These are that the diaphragm is already working hard and well trained in emphysema, with a shift towards fatigue resistant type I fibres 2, that at a single fibre level it is energetically more efficient 3, that (allowing for hyperinflation) it is not actually weak 4, 5 and that diaphragm fatigue cannot be elicited in patients in vivo 6, 7, even when patients are sufficiently ill to require mechanical ventilation 8. The question of whether the respiratory muscles are weak in COPD seems particularly important in the context of IMT. In the current issue of the European Respiratory Journal, Gosselink et al. 9 cite our paper 5 as evidence that the diaphragm is weak; in fact, we concluded that the major reason for the reduced transdiaphragmatic pressures observed in COPD was hyperinflation, which of course would not be expected to improve with IMT. They also state that inspiratory muscle weakness contributes to a range of poor outcomes in COPD, whereas in our view associations between reduced inspiratory pressures due to hyperinflation and poor outcomes may simply be epiphenomena. Thus, for example, in a recent survival analysis 10 we found that both inspiratory muscle strength and hyperinflation predicted death in a substantially similar way, probably because they measured different properties of the same thing. In fact, inspiratory muscle strength proved statistically, but not clinically, superior with an area under the curve on a receiver operating characteristic plot of 0.68 versus 0.62 compared with inspiratory capacity/total lung capacity ratio, but the possible technical factors, notably transmission of pressure within the emphysematous lung, underlying this are beyond the scope of this editorial.

Inspiratory muscle training is usually considered to have its origins in the now classic paper by Leith and Bradley 11, in which 12 normal subjects were randomised into three groups of four to receive no treatment, or training for strength or for endurance. The strength group increased their maximal inspiratory pressure (PI,max) by an impressive 55% (more of this below). In the present issue, Gosselink et al. 9 conducted an exhaustive review of the English and non-English language literature in order to update their 2002 meta-analysis 12. They conclude that statistically significant and clinically relevant improvements were observed for inspiratory muscle strength and endurance, functional exercise capacity, and dyspnoea and quality of life indices. However, this conclusion comes with some health warnings.

First, although we accept that IMT can be associated with structural changes in the inspiratory muscles 13, Gosselink et al. 9 did not exclude from their meta-analysis studies with other factors which might have biased the results. Of these the most important is lack of a sham control, without which the placebo effect might be particularly strong for measures of dyspnoea and quality of life indices. Patient assessed outcomes have been shown to improve following interventions without a known aetiological mechanism, including osteopathy (even though flow limitation also worsened in the treatment group) 14, listening to music for 30 min 15, singing 16, as well as a humour intervention by a clown which improved a “cheerfulness index” 17. It is therefore plausible that outcomes might also improve through a placebo type mechanism after IMT. Consistent with this proposition the patients studied by Ramirez-Sarmiento et al. 13 failed to improve their 6-min walk distance (6MWD) or maximal oxygen uptake despite a 12 cmH2O increase in PI,max and histological improvement in their inspiratory muscles.

Secondly, the first two outcomes (strength and endurance) are not directly relevant to the patient experience, in the sense that patients do not present to their physicians with difficulty completing respiratory muscle assessments. Moreover, technique is critically important in performing voluntary tests of maximal strength and endurance. We explored this in detail in a (admittedly small) study in normal subjects who were allocated to receive either real or sham IMT 18. Consistent with other reports the treatment group improved PI,max but their twitch transdiaphragmatic pressure failed to improve, leading us to infer that they had simply “got better at doing the test” 19. We also found that they improved their inspiratory muscle endurance; however, when analysed using a technique which accounted for breathing pattern 20, it was found that their apparent improvement simply reflected a more efficient breathing pattern 21. A further example of “getting better at doing the test” is provided by one of us (M. Green) who was a (then) naïve subject in the 1976 Leith and Bradley 11 study. He was randomised to strength training and showed an impressive improvement in strength. M. Green participated intermittently in studies requiring respiratory muscle strength measurement in our laboratory between that time and until his retirement from academic work in 2001. Over 25 years he found that the improvement in PI,max documented following “strength training” in 1976 never wore off, suggesting that the improvement recorded by Leith and Bradley 11 was due to improved test technique rather than as a result of true increase in muscle strength!

The only outcomes currently accepted as valid for COPD by regulatory agencies in Europe and the USA are forced expiratory volume in 1 s, exacerbation and death; however, 6MWD is accepted in other diseases (such as pulmonary hypertension) and thus logically could in future be accepted for COPD. Until recently the minimal clinically important difference (MCID) for the 6MWD was considered to be 54 m 22. More recently this has been reduced to either 35 m 23 or 25 m 24. Only with the latter threshold does the improvement shown in the current meta-analysis (32 m) exceed the MCID, and then only by 7 m, scarcely clinically significant. Careful review of the data of Holland et al. 24, who derived their figures by analysing the benefit conferred by a PR course, showed that patients who experienced no detectable benefit increased 6MWD by a mean of 17 m, while those who perceived a “small” benefit had a mean increase in 6MWD of 60 m. We also note that, in the current meta-analysis, the subanalysis of patients receiving PR alone compared to IMT in addition to PR failed to demonstrate significant improvement (fig. 4 of Gosselink et al. 9). Since PR is a therapy of proven benefit these data would suggest that IMT has little additional to offer.

In conclusion, we congratulate Gosselink et al. 9 for their comprehensive review and analysis of the literature. We interpret their data as showing that when given alone IMT is of marginal clinical benefit in COPD, and that it offers no additional value to PR; indeed, by committing the time of both patients and their rehabilitation team, IMT may distract from PR itself. We suggest that future studies do not attempt to measure inspiratory muscle strength or endurance but that the primary measure should reflect a patient focused outcome, such as a field walking test or physical activity monitoring.

Footnotes

  • Support Statement

    The NIHR Respiratory Biomedical Research Unit at the Royal Brompton Hospital and National Heart and Lung Institute (Imperial College) part fund M.I. Polkey's salary.

  • Statement of Interest

    None declared.

  • ©ERS 2011

REFERENCES

  1. ↵
    1. Griffiths TL,
    2. Burr ML,
    3. Campbell IA,
    4. et al
    . Results at 1 year of outpatient multidisciplinary pulmonary rehabilitation: a randomised controlled trial. Lancet 2000; 355: 362–368.
    OpenUrlCrossRefPubMedWeb of Science
  2. ↵
    1. Levine S,
    2. Kaiser L,
    3. Leferovich J,
    4. et al
    . Cellular adaptations in the diaphragm in chronic obstructive pulmonary disease. N Engl J Med 1997; 337: 1799–1806.
    OpenUrlCrossRefPubMedWeb of Science
  3. ↵
    1. Stubbings AK,
    2. Moore AJ,
    3. Dusmet M,
    4. et al
    . Physiological properties of human diaphragm muscle fibres and the effect of chronic obstructive pulmonary disease. J Physiol 2008; 586: 2637–2650.
    OpenUrlCrossRefPubMedWeb of Science
  4. ↵
    1. Similowski T,
    2. Yan S,
    3. Gauthier AP,
    4. et al
    . Contractile properties of the human diaphragm during chronic hyperinflation. N Engl J Med 1991; 325: 917–923.
    OpenUrlCrossRefPubMedWeb of Science
  5. ↵
    1. Polkey MI,
    2. Kyroussis D,
    3. Hamnegard C-H,
    4. et al
    . Diaphragm strength in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1996; 154: 1310–1317.
    OpenUrlCrossRefPubMedWeb of Science
  6. ↵
    1. Polkey MI,
    2. Kyroussis D,
    3. Hamnegard C-H,
    4. et al
    . Diaphragm performance during maximal voluntary ventilation in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1997; 155: 642–648.
    OpenUrlCrossRefPubMedWeb of Science
  7. ↵
    1. Polkey MI,
    2. Kyroussis D,
    3. Keilty SEJ,
    4. et al
    . Exhaustive treadmill exercise does not reduce twitch transdiaphragmatic pressure in patients with COPD. Am J Respir Crit Care Med 1995; 152: 959–964.
    OpenUrlCrossRefPubMedWeb of Science
  8. ↵
    1. Laghi F,
    2. Cattapan SE,
    3. Jubran A,
    4. et al
    . Is weaning failure caused by low-frequency fatigue of the diaphragm? Am J Respir Crit Care Med 2003; 167: 120–127.
    OpenUrlCrossRefPubMedWeb of Science
  9. ↵
    1. Gosselink R,
    2. De Vos J,
    3. van denHeuvel SP,
    4. et al
    . Impact of inspiratory muscle training in patients with COPD: what is the evidence? Eur Respir J 2011; 37: 416–425.
    OpenUrlAbstract/FREE Full Text
  10. ↵
    1. Moore AJ,
    2. Soler RS,
    3. Cetti EJ,
    4. et al
    . Sniff nasal inspiratory pressure versus IC/TLC ratio as predictors of mortality in COPD. Respir Med 2010; 104: 1319–1325.
    OpenUrlCrossRefPubMedWeb of Science
  11. ↵
    1. Leith DE,
    2. Bradley M
    Ventilatory muscle strength endurance training. J Appl Physiol 1976; 41: 508–516.
    OpenUrlAbstract/FREE Full Text
  12. ↵
    1. Lötters F,
    2. van Tol B,
    3. Kwakkel G,
    4. et al
    . Effects of controlled inspiratory muscle training in patients with COPD: a meta-analysis. Eur Respir J 2002; 20: 570–577.
    OpenUrlAbstract/FREE Full Text
  13. ↵
    1. Ramirez-Sarmiento A,
    2. Orozco-Levi M,
    3. Guell R,
    4. et al
    . Inspiratory muscle training in patients with chronic obstructive pulmonary disease: structural adaptation and physiologic outcomes. Am J Respir Crit Care Med 2002; 166: 1491–1497.
    OpenUrlCrossRefPubMedWeb of Science
  14. ↵
    1. Noll DR,
    2. Degenhardt BF,
    3. Johnson JC,
    4. et al
    . Immediate effects of osteopathic manipulative treatment in elderly patients with chronic obstructive pulmonary disease. J Am Osteopath Assoc 2008; 108: 251–259.
    OpenUrlPubMed
  15. ↵
    1. Singh VP,
    2. Rao V,
    3. Prem V,
    4. et al
    . Comparison of the effectiveness of music and progressive muscle relaxation for anxiety in COPD: a randomized controlled pilot study. Chron Respir Dis 2009; 6: 209–216.
    OpenUrlAbstract/FREE Full Text
  16. ↵
    1. Bonilha AG,
    2. Onofre F,
    3. Vieira ML,
    4. et al
    . Effects of singing classes on pulmonary function and quality of life of COPD patients. Int J Chron Obstruct Pulmon Dis 2009; 4: 1–8.
    OpenUrlPubMed
  17. ↵
    1. Brutsche MH,
    2. Grossman P,
    3. Muller RE,
    4. et al
    . Impact of laughter on air trapping in severe chronic obstructive lung disease. Int J Chron Obstruct Pulmon Dis 2008; 3: 185–192.
    OpenUrlPubMed
  18. ↵
    1. Hart N,
    2. Sylvester K,
    3. Ward S,
    4. et al
    . Evaluation of an inspiratory muscle trainer in healthy humans. Respir Med 2001; 95: 526–531.
    OpenUrlCrossRefPubMedWeb of Science
  19. ↵
    1. Polkey MI,
    2. Moxham J
    . Improvement in volitional tests of muscle function alone may not be adequate evidence that inspiratory muscle training is effective. Eur Respir J 2004; 23: 5–6.
    OpenUrlFREE Full Text
  20. ↵
    1. Hart N,
    2. Hawkins P,
    3. Hamnegård C-H,
    4. et al
    . A novel clinical test of respiratory muscle endurance. Eur Respir J 2002; 19: 232–239.
    OpenUrlAbstract/FREE Full Text
  21. ↵
    1. Hart N,
    2. Moxham J,
    3. Polkey MI
    . Inspiratory muscle training as a tool for the management of patients with COPD. Eur Respir J 2004; 24: 511–
    OpenUrlFREE Full Text
  22. ↵
    1. Redelmeier DA,
    2. Bayoumi AM,
    3. Goldstein RS,
    4. et al
    . Interpreting small differences in functional status: the six minute walk test in chronic lung disease patients. Am J Respir Crit Care Med 1997; 155: 1278–1282.
    OpenUrlCrossRefPubMedWeb of Science
  23. ↵
    1. Puhan MA,
    2. Mador MJ,
    3. Held U,
    4. et al
    . Interpretation of treatment changes in 6-minute walk distance in patients with COPD. Eur Respir J 2008; 32: 637–643.
    OpenUrlAbstract/FREE Full Text
  24. ↵
    1. Holland AE,
    2. Hill CJ,
    3. Rasekaba T,
    4. et al
    . Updating the minimal important difference for six-minute walk distance in patients with chronic obstructive pulmonary disease. Arch Phys Med Rehabil 2010; 91: 221–225.
    OpenUrlCrossRefPubMedWeb of Science
View Abstract
Previous
Back to top
View this article with LENS
Vol 37 Issue 2 Table of Contents
European Respiratory Journal: 37 (2)
  • Table of Contents
  • Table of Contents (PDF)
  • About the Cover
  • Index by author
Email

Thank you for your interest in spreading the word on European Respiratory Society .

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
The case against inspiratory muscle training in COPD
(Your Name) has sent you a message from European Respiratory Society
(Your Name) thought you would like to see the European Respiratory Society web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Print
Citation Tools
The case against inspiratory muscle training in COPD
M.I. Polkey, J. Moxham, M. Green
European Respiratory Journal Feb 2011, 37 (2) 236-237; DOI: 10.1183/09031936.00095510

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero

Share
The case against inspiratory muscle training in COPD
M.I. Polkey, J. Moxham, M. Green
European Respiratory Journal Feb 2011, 37 (2) 236-237; DOI: 10.1183/09031936.00095510
del.icio.us logo Digg logo Reddit logo Technorati logo Twitter logo CiteULike logo Connotea logo Facebook logo Google logo Mendeley logo
Full Text (PDF)

Jump To

  • Article
    • Footnotes
    • REFERENCES
  • Info & Metrics
  • PDF

Subjects

  • COPD and smoking
  • Tweet Widget
  • Facebook Like
  • Google Plus One

More in this TOC Section

  • The case for inspiratory muscle training in COPD
  • Rhinovirus vaccination: the case in favour
Show more Pro and Con Editorial

Related Articles

Navigate

  • Home
  • Current issue
  • Archive

About the ERJ

  • Journal information
  • Editorial board
  • Reviewers
  • Press
  • Permissions and reprints
  • Advertising

The European Respiratory Society

  • Society home
  • myERS
  • Privacy policy
  • Accessibility

ERS publications

  • European Respiratory Journal
  • ERJ Open Research
  • European Respiratory Review
  • Breathe
  • ERS books online
  • ERS Bookshop

Help

  • Feedback

For authors

  • Instructions for authors
  • Publication ethics and malpractice
  • Submit a manuscript

For readers

  • Alerts
  • Subjects
  • Podcasts
  • RSS

Subscriptions

  • Accessing the ERS publications

Contact us

European Respiratory Society
442 Glossop Road
Sheffield S10 2PX
United Kingdom
Tel: +44 114 2672860
Email: journals@ersnet.org

ISSN

Print ISSN:  0903-1936
Online ISSN: 1399-3003

Copyright © 2022 by the European Respiratory Society