The effect of inspiratory resistive training on exercise capacity in optimally treated patients with severe chronic airflow limitation

Inspiratory muscle training, with or without concomitant pulmonary rehabilitation, for chronic obstructive pulmonary disease (COPD)

BACKGROUND

Inspiratory muscle training (IMT) aims to improve respiratory muscle strength and endurance. Clinical trials used various training protocols, devices and respiratory measurements to check the effectiveness of this intervention. The current guidelines reported a possible advantage of IMT, particularly in people with respiratory muscle weakness. However, it remains unclear to what extent IMT is clinically beneficial, especially when associated with pulmonary rehabilitation (PR).   OBJECTIVES: To assess the effect of inspiratory muscle training (IMT) on chronic obstructive pulmonary disease (COPD), as a stand-alone intervention and when combined with pulmonary rehabilitation (PR).

SEARCH METHODS

We searched the Cochrane Airways trials register, CENTRAL, MEDLINE, Embase, PsycINFO, Cumulative Index to Nursing and Allied Health Literature (CINAHL) EBSCO, Physiotherapy Evidence Database (PEDro) ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform on 20 October 2021. We also checked reference lists of all primary studies and review articles.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared IMT in combination with PR versus PR alone and IMT versus control/sham. We included different types of IMT irrespective of the mode of delivery. We excluded trials that used resistive devices without controlling the breathing pattern or a training load of less than 30% of maximal inspiratory pressure (PImax), or both.

DATA COLLECTION AND ANALYSIS

We used standard methods recommended by Cochrane including assessment of risk of bias with RoB 2. Our primary outcomes were dyspnea, functional exercise capacity and health-related quality of life.  MAIN RESULTS: We included 55 RCTs in this review. Both IMT and PR protocols varied significantly across the trials, especially in training duration, loads, devices, number/ frequency of sessions and the PR programs. Only eight trials were at low risk of bias. PR+IMT versus PR We included 22 trials (1446 participants) in this comparison. Based on a minimal clinically important difference (MCID) of -1 unit, we did not find an improvement in dyspnea assessed with the Borg scale at submaximal exercise capacity (mean difference (MD) 0.19, 95% confidence interval (CI) -0.42 to 0.79; 2 RCTs, 202 participants; moderate-certainty evidence).   We also found no improvement in dyspnea assessed with themodified Medical Research Council dyspnea scale (mMRC) according to an MCID between -0.5 and -1 unit (MD -0.12, 95% CI -0.39 to 0.14; 2 RCTs, 204 participants; very low-certainty evidence).  Pooling evidence for the 6-minute walk distance (6MWD) showed an increase of 5.95 meters (95% CI -5.73 to 17.63; 12 RCTs, 1199 participants; very low-certainty evidence) and failed to reach the MCID of 26 meters. In subgroup analysis, we divided the RCTs according to the training duration and mean baseline PImax. The test for subgroup differences was not significant. Trials at low risk of bias (n = 3) demonstrated a larger effect estimate than the overall. The summary effect of the St George's Respiratory Questionnaire (SGRQ) revealed an overall total score below the MCID of 4 units (MD 0.13, 95% CI -0.93 to 1.20; 7 RCTs, 908 participants; low-certainty evidence).  The summary effect of COPD Assessment Test (CAT) did not show an improvement in the HRQoL (MD 0.13, 95% CI -0.80 to 1.06; 2 RCTs, 657 participants; very low-certainty evidence), according to an MCID of -1.6 units.  Pooling the RCTs that reported PImax showed an increase of 11.46 cmH₂O (95% CI 7.42 to 15.50; 17 RCTs, 1329 participants; moderate-certainty evidence) but failed to reach the MCID of 17.2 cmH₂O.  In subgroup analysis, we did not find a difference between different training durations and between studies judged with and without respiratory muscle weakness.  One abstract reported some adverse effects that were considered "minor and self-limited". IMT versus control/sham Thirty-seven RCTs with 1021 participants contributed to our second comparison. There was a trend towards an improvement when Borg was calculated at submaximal exercise capacity (MD -0.94, 95% CI -1.36 to -0.51; 6 RCTs, 144 participants; very low-certainty evidence). Only one trial was at a low risk of bias. Eight studies (nine arms) used the Baseline Dyspnea Index - Transition Dyspnea Index (BDI-TDI). Based on an MCID of +1 unit, they showed an improvement only with the 'total score' of the TDI (MD 2.98, 95% CI 2.07 to 3.89; 8 RCTs, 238 participants; very low-certainty evidence). We did not find a difference between studies classified as with and without respiratory muscle weakness. Only one trial was at low risk of bias. Four studies reported the mMRC, revealing a possible improvement in dyspnea in the IMT group (MD -0.59, 95% CI -0.76 to -0.43; 4 RCTs, 150 participants; low-certainty evidence). Two trials were at low risk of bias. Compared to control/sham, the MD in the 6MWD following IMT was 35.71 (95% CI 25.68 to 45.74; 16 RCTs, 501 participants; moderate-certainty evidence). Two studies were at low risk of bias. In subgroup analysis, we did not find a difference between different training durations and between studies judged with and without respiratory muscle weakness.  Six studies reported theSGRQ total score, showing a larger effect in the IMT group (MD -3.85, 95% CI -8.18 to 0.48; 6 RCTs, 182 participants; very low-certainty evidence). The lower limit of the 95% CI exceeded the MCID of -4 units. Only one study was at low risk of bias. There was an improvement in life quality with CAT (MD -2.97, 95% CI -3.85 to -2.10; 2 RCTs, 86 participants; moderate-certainty evidence). One trial was at low risk of bias. Thirty-two RCTs reported PImax, showing an improvement without reaching the MCID (MD 14.57 cmH₂O, 95% CI 9.85 to 19.29; 32 RCTs, 916 participants; low-certainty evidence). In subgroup analysis, we did not find a difference between different training durations and between studies judged with and without respiratory muscle weakness.   None of the included RCTs reported adverse events.

AUTHORS' CONCLUSIONS

IMT may not improve dyspnea, functional exercise capacity and life quality when associated with PR. However, IMT is likely to improve these outcomes when provided alone. For both interventions, a larger effect in participants with respiratory muscle weakness and with longer training durations is still to be confirmed.

Supported self-management for patients with moderate to severe chronic obstructive pulmonary disease (COPD): an evidence synthesis and economic analysis

BACKGROUND

Self-management (SM) support for patients with chronic obstructive pulmonary disease (COPD) is variable in its coverage, content, method and timing of delivery. There is insufficient evidence for which SM interventions are the most effective and cost-effective.

OBJECTIVES

To undertake (1) a systematic review of the evidence for the effectiveness of SM interventions commencing within 6 weeks of hospital discharge for an exacerbation for COPD (review 1); (2) a systematic review of the qualitative evidence about patient satisfaction, acceptance and barriers to SM interventions (review 2); (3) a systematic review of the cost-effectiveness of SM support interventions within 6 weeks of hospital discharge for an exacerbation of COPD (review 3); (4) a cost-effectiveness analysis and economic model of post-exacerbation SM support compared with usual care (UC) (economic model); and (5) a wider systematic review of the evidence of the effectiveness of SM support, including interventions (such as pulmonary rehabilitation) in which there are significant components of SM, to identify which components are the most important in reducing exacerbations, hospital admissions/readmissions and improving quality of life (review 4).

METHODS

The following electronic databases were searched from inception to May 2012: MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and Science Citation Index [Institute of Scientific Information (ISI)]. Subject-specific databases were also searched: PEDro physiotherapy evidence database, PsycINFO and the Cochrane Airways Group Register of Trials. Ongoing studies were sourced through the metaRegister of Current Controlled Trials, International Standard Randomised Controlled Trial Number database, World Health Organization International Clinical Trials Registry Platform Portal and ClinicalTrials.gov. Specialist abstract and conference proceedings were sourced through ISI's Conference Proceedings Citation Index and British Library's Electronic Table of Contents (Zetoc). Hand-searching through European Respiratory Society, the American Thoracic Society and British Thoracic Society conference proceedings from 2010 to 2012 was also undertaken, and selected websites were also examined. Title, abstracts and full texts of potentially relevant studies were scanned by two independent reviewers. Primary studies were included if ≈90% of the population had COPD, the majority were of at least moderate severity and reported on any intervention that included a SM component or package. Accepted study designs and outcomes differed between the reviews. Risk of bias for randomised controlled trials (RCTs) was assessed using the Cochrane tool. Random-effects meta-analysis was used to combine studies where appropriate. A Markov model, taking a 30-year time horizon, compared a SM intervention immediately following a hospital admission for an acute exacerbation with UC. Incremental costs and quality-adjusted life-years were calculated, with sensitivity analyses.

RESULTS

From 13,355 abstracts, 10 RCTs were included for review 1, one study each for reviews 2 and 3, and 174 RCTs for review 4. Available studies were heterogeneous and many were of poor quality. Meta-analysis identified no evidence of benefit of post-discharge SM support on admissions [hazard ratio (HR) 0.78, 95% confidence interval (CI) 0.52 to 1.17], mortality (HR 1.07, 95% CI 0.74 to 1.54) and most other health outcomes. A modest improvement in health-related quality of life (HRQoL) was identified but this was possibly biased due to high loss to follow-up. The economic model was speculative due to uncertainty in impact on readmissions. Compared with UC, post-discharge SM support (delivered within 6 weeks of discharge) was more costly and resulted in better outcomes (£683 cost difference and 0.0831 QALY gain). Studies assessing the effect of individual components were few but only exercise significantly improved HRQoL (3-month St George's Respiratory Questionnaire 4.87, 95% CI 3.96 to 5.79). Multicomponent interventions produced an improved HRQoL compared with UC (mean difference 6.50, 95% CI 3.62 to 9.39, at 3 months). Results were consistent with a potential reduction in admissions. Interventions with more enhanced care from health-care professionals improved HRQoL and reduced admissions at 1-year follow-up. Interventions that included supervised or unsupervised structured exercise resulted in significant and clinically important improvements in HRQoL up to 6 months.

LIMITATIONS

This review was based on a comprehensive search strategy that should have identified most of the relevant studies. The main limitations result from the heterogeneity of studies available and widespread problems with their design and reporting.

CONCLUSIONS

There was little evidence of benefit of providing SM support to patients shortly after discharge from hospital, although effects observed were consistent with possible improvement in HRQoL and reduction in hospital admissions. It was not easy to tease out the most effective components of SM support packages, although interventions containing exercise seemed the most effective. Future work should include qualitative studies to explore barriers and facilitators to SM post exacerbation and novel approaches to affect behaviour change, tailored to the individual and their circumstances. Any new trials should be properly designed and conducted, with special attention to reducing loss to follow-up. Individual participant data meta-analysis may help to identify the most effective components of SM interventions.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42011001588.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Inspiratory muscle training for asthma

BACKGROUND

In some people with asthma, expiratory airflow limitation, premature closure of small airways, activity of inspiratory muscles at the end of expiration and reduced pulmonary compliance may lead to lung hyperinflation. With the increase in lung volume, chest wall geometry is modified, shortening the inspiratory muscles and leaving them at a sub-optimal position in their length-tension relationship. Thus, the capacity of these muscles to generate tension is reduced. An increase in cross-sectional area of the inspiratory muscles caused by hypertrophy could offset the functional weakening induced by hyperinflation. Previous studies have shown that inspiratory muscle training promotes diaphragm hypertrophy in healthy people and patients with chronic heart failure, and increases the proportion of type I fibres and the size of type II fibres of the external intercostal muscles in patients with chronic obstructive pulmonary disease. However, its effects on clinical outcomes in patients with asthma are unclear.

OBJECTIVES

To evaluate the efficacy of inspiratory muscle training with either an external resistive device or threshold loading in people with asthma.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register of trials, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov and reference lists of included studies. The latest search was performed in November 2012.

SELECTION CRITERIA

We included randomised controlled trials that involved the use of an external inspiratory muscle training device versus a control (sham or no inspiratory training device) in people with stable asthma.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included five studies involving 113 adults. Participants in four studies had mild to moderate asthma and the fifth study included participants independent of their asthma severity. There were substantial differences between the studies, including the training protocol, duration of training sessions (10 to 30 minutes) and duration of the intervention (3 to 25 weeks). Three clinical trials were produced by the same research group. Risk of bias in the included studies was difficult to ascertain accurately due to poor reporting of methods.The included studies showed a statistically significant increase in inspiratory muscle strength, measured by maximal inspiratory pressure (PImax) (mean difference (MD) 13.34 cmH2O, 95% CI 4.70 to 21.98, 4 studies, 84 participants, low quality evidence). Our other primary outcome, exacerbations requiring a course of oral or inhaled corticosteroids or emergency department visits, was not reported. For the secondary outcomes, results from one trial showed no statistically significant difference between the inspiratory muscle training group and the control group for maximal expiratory pressure, peak expiratory flow rate, forced expiratory volume in one second, forced vital capacity, sensation of dyspnoea and use of beta2-agonist. There were no studies describing inspiratory muscle endurance, hospital admissions or days off work or school.

AUTHORS' CONCLUSIONS

There is no conclusive evidence in this review to support or refute inspiratory muscle training for asthma. The evidence was limited by the small number of trials with few participants together with the risk of bias. More well conducted randomised controlled trials are needed. Future trials should investigate the following outcomes: lung function, exacerbation rate, asthma symptoms, hospital admissions, use of medications and days off work or school. Inspiratory muscle training should also be assessed in people with more severe asthma and conducted in children with asthma.

Inspiratory muscle training in adults with chronic obstructive pulmonary disease: a systematic review

The purpose of this study was to conduct a systematic review to determine the effect of inspiratory muscle training (IMT) on inspiratory muscle strength and endurance, exercise capacity, dyspnea and quality of life for adults with chronic obstructive pulmonary disease (COPD). A systematic review of the literature was conducted according the Cochrane Collaboration protocol using Medline and CINAHL. Nineteen of 274 extracted articles met the inclusion criteria and addressed comparisons of interest which included: IMT versus sham; IMT versus no intervention; low- versus high-intensity IMT; and two different modes of IMT. Thirteen meta-analyses were reported. Results indicate that targeted resistive or threshold IMT was associated with significant improvements in some outcomes of inspiratory muscle strength (PI(max) (cm H2O)) and endurance (Inspiratory Threshold Loading (kPa)), exercise capacity (Borg Scale for Respiratory Effort (modified Borg scale), Work Rate maximum (Watts)), and dyspnea (Transition Dyspnea Index), whereas IMT without a target or not using threshold training did not show improvement in these variables. There was no conclusive evidence regarding quality of life measures. IMT is effective for adults with COPD when using threshold or targeted devices that control or provide a target for training intensity.

Inspiratory muscle training for asthma

BACKGROUND

In moderate to severe chronic obstructive pulmonary disease there is good evidence of a generalised loss of muscle bulk (including the respiratory muscles). It is possible that similar loss of respiratory muscle strength occur particularly in more severe asthma related in part to the effects of steroid therapy. Thus the respiratory muscle function may well be of relevance in asthma and if dysfunctional, may be a suitable target for training.

OBJECTIVES

To evaluate the efficacy of inspiratory muscle training with an external resistive device in patients with asthma.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2002), MEDLINE (January 1966 to March 2002), EMBASE (January 1985 to March 2002), CINAHL (to March 2002) and the UK National Research Register of trials (January 1982 to March 2002) and reference lists of articles. We also searched on line respiratory journals and contacted manufacturers of training devices to obtain trials.

SELECTION CRITERIA

All randomised-controlled trials that involved the use of an external inspiratory muscle training device versus a control (sham or no inspiratory training device) were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected articles for inclusion, evaluated methodological quality of the studies and abstracted data.

MAIN RESULTS

Five studies were included in the review with four of the studies being produced by the same group. PI(max) (maximum inspiratory pressure) reported in three studies with 76 patients showed significant improvement with inspiratory muscle training when compared to the control group (WMD 23.07 cmH(2)O, 95%CI 15.65 to 30.50). Unfortunately, due to the paucity of included studies and data no other outcome was reported by more than one study. Therefore it is not possible to confirm whether this increase seen with PI(max) translates into any measurable clinical benefit.

REVIEWER'S CONCLUSIONS

Currently there is insufficient evidence to suggest that inspiratory muscle training provides any clinical benefit to patients with asthma. Due to the limited availability of studies in this area there is a need for further trials evaluating the efficacy of inspiratory muscle training devices in patients with asthma. These studies should investigate asthmatics with a range of severity. They should investigate clinically relevant outcomes such as lung function, symptoms, exacerbation rate and concomitant medications.

Controlled trial of respiratory muscle training in chronic airflow limitation

BACKGROUND

Whether respiratory muscle training is of benefit to patients with chronic airflow limitation is controversial. The objective of the study was to determine the effect of resistance breathing training on physiological and functional measures in patients with chronic airflow obstruction.

METHODS

The design was a randomised, double blind, controlled trial with a six month follow up. Eighty two patients with a forced expiratory volume in one second (FEV1) of less than 70% predicted, and an FEV1/vital capacity ratio of less than 0.7, were randomised to receive training for 10 minutes five times daily with progressively larger resistances through a resistive breathing device (PFLEX) as tolerated or to a sham device which gave minimal resistance. The main outcome measures, respiratory muscle strength and endurance, a progressive exercise test, a six minute walk test and physical and emotional function (chronic respiratory questionnaire) were assessed at monthly intervals. Patients in both groups were also randomised to wear or not wear nose clips during their training.

RESULTS

No significant differences were observed between treatment and control groups, with or without nose clips, for any of the outcomes. Confidence intervals on the difference between treatments were narrow, excluding clinically important difference in any major outcome.

CONCLUSION

This training regimen fails to strengthen respiratory muscles or improve exercise or functional capacity in patients with chronic airflow limitation.

Respiratory muscle training in chronic airflow limitation: a meta-analysis

The purpose of this study was to determine the effect of respiratory muscle training on muscle strength and endurance, exercise capacity, and functional status in patients with chronic airflow limitation. Computerized bibliographic data bases (MEDLINE AND SCISEARCH) were searched for published clinical trails, and an independent review of 73 articles by two of the investigators identified 17 relevant randomized trials for inclusion. Study quality was assessed and descriptive information concerning the study populations, interventions, and outcome measurements was extracted. We combined effect sizes across studies (the difference between treatment and control groups divided by the pooled standard deviation of the outcome measure). Across all studies, the effect sizes and associated p-values were as follows: maximal inspiratory pressure 0.12, p = 0.38; maximal voluntary ventilation 0.43, p = 0.02; respiratory muscle endurance 0.21, p = 0.14; laboratory exercise capacity -0.01, p = 0.43; functional exercise capacity 0.20, p = 0.15; functional status 0.06, p = 0.72. Secondary analyses suggested that endurance and function may be improved if resistance training with control of breathing pattern is undertaken. Overall, there is little evidence of clinically important benefit of respiratory muscle training in patients with with chronic airflow limitation. The possibility that benefit may result if resistance training is conducted in a fashion that ensures generation of adequate mouth pressures may be worthy of further study.

Upper-limb and lower-limb exercise training in patients with chronic airflow obstruction

We designed a randomized controlled study to evaluate the benefit of upper-limb exercise training, alone and in combination with walking training, in patients with severe CAO. In an outpatient department supervised by a physiotherapist, we evaluated 28 patients with severe stable CAO (FEV1, 32 percent of predicted). Patients were randomly allocated to either a control (eight), upper-limb (six), lower-limb (seven), or combined (seven) exercise group. The upper-limb group trained with a circuit of upper-limb exercises, the lower-limb group by walking, and the combined group with both. Exercise was for one hour three times per week for eight weeks. Assessment before and after training included pulmonary function, mouth pressures, respiratory muscle endurance, maximal bicycle exercise test, maximal and submaximal arm ergometer, six-minute walking distance, and a scale of well-being (Bandura scale). Twenty-six patients completed the program. There was a significant improvement (Wilcoxon rank sum test) in the following: six-minute walking distance in the lower-limb (p less than 0.005) and combined (p less than 0.003) groups; arm ergometer in the upper-limb (p less than 0.005) and combined (p less than 0.04) groups; and the scale of well-being in the combined (p less than 0.005) group. There was no significant change in any other parameter measured. We conclude that exercise training improves exercise performance in severe CAO, that the training is specific for the muscle group trained, and that upper-limb exercises should be included in training programs for these patients.