Efficacy of inspiratory muscle training in chronic heart failure patients: A systematic review and meta-analysis

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Abstract

Introduction

Inspiratory muscle training (IMT) offers an alternative to exercise training (ExT) in the most severely deconditioned heart failure patients who are unable to exercise. We conducted a meta-analysis to determine magnitude of change in peak VO2, six minute walk distance (6MWD), Quality of Life measured by the Minnesota Living with Heart Failure Questionnaire (MLWHFQ), maximal inspiratory pressure (PI max) and ventilatory equivalent for carbon dioxide (VE/VCO2 slope) with IMT.

Methods

A systematic search was conducted of randomized, controlled trials of IMT therapy in CHF patients using Medline (Ovid) (1950–February 2012), Embase.com (1974–February 2012), Cochrane Central Register of Controlled Trials and CINAHL (1981–February 2012). The search strategy included a mix of MeSH and free text terms for the key concepts heart failure, inspiratory or respiratory muscle training, exercise training

Results

The eleven included studies contained data on 287 participants: 148 IMT participants and 139 sham or sedentary control. Compared to control groups, CHF patients undergoing IMT showed a significant improvement in peak VO2 (+ 1.83 ml kg 1 min 1, 95% C.I. 1.33 to 2.32 ml kg 1 min 1, p < 0.00001); 6MWD (+ 34.35 m, 95% C.I. 22.45 to 46.24 m, p < 0.00001); MLWHFQ (− 12.25, 95% C.I. − 17.08 to − 7.43, p < 0.00001); PImax (+ 20.01, 95% C.I. 13.96 to 26.06, p < 0.00001); and VE/VCO2 slope (− 2.28, 95% C.I. − 3.25 to − 1.30, p < 0.00001).

Conclusions

IMT improves cardio-respiratory fitness and quality of life to a similar magnitude to conventional exercise training and may provide an initial alternative to the more severely de-conditioned CHF patients who may then transition to conventional ExT.

Introduction

Although considerable progress has been made in optimizing drug management of patients with chronic heart failure (CHF), the social and personal burden of CHF is still characterized by debilitating symptoms, frequent re-hospitalizations and high mortality rates [1]. A specific symptom of CHF is respiratory muscle fatigue due to frequent dyspnea [2]. Exercise-based cardiac rehabilitation is a comprehensive structured intervention since it best addresses the complex interplay of medical, psychological and behavioural factors facing CHF patients [3]. However, some patients do not adapt or drop out of conventional exercise training programs, and others are unable to perform even low levels of physical effort. The most severely impaired patients (New York Heart Association (NYHA) class III/IV) may be, at least initially, exercise intolerant, therefore alternative physical therapies have been employed including functional electrical stimulation [4] and respiratory (inspiratory) muscle training [5].

Respiratory, or inspiratory, muscle training (IMT) has shown potential beneficial effects in CHF patients, such as improving peak oxygen consumption (VO2) [6], better performance in functional tests [7], and improved quality of life [8]. IMT therapy may be an alternative treatment for patients who cannot engage in conventional exercise training programs, but the beneficial effects of IMT in the treatment of patients with CHF have yet to be compared to traditional aerobic exercise training programs. Published studies comparing benefits derived from IMT therapy mostly exhibit small sample sizes and somewhat conflicting results. The aim of this work was to conduct a systematic review and meta-analysis of randomized, controlled trials of IMT versus sham or sedentary control. We examined the magnitude of change in peak VO2, six minute walk distance (6MWD), Quality of Life measured by the Minnesota Living with Heart Failure Questionnaire (MLHFQ), maximal inspiratory pressure (PImax) and of the slope of increase in ventilation over carbon dioxide output (VE/VCO2 slope), comparing the effect sizes with those previously reported following conventional aerobic or resistance exercise training in this patient population.

Section snippets

Search strategy

Potential studies were identified by a systematic review librarian. A systematic search was conducted of Medline (Ovid) (1950–February 2012), Embase.com (1974–February 2012), Cochrane Central Register of Controlled Trials and CINAHL (1981–February 2012). The search strategy included a mix of MeSH and free text terms for the key concepts heart failure, inspiratory or respiratory muscle training, exercise training, and these were combined with a sensitive search strategy to identify randomized

Results

The eleven included studies [6], [7], [8], [12], [13], [14], [15], [16], [17], [18], [19] contained data of 287 patients: 148 IMT participants and 139 sham or sedentary control participants. Generally, the studies were well matched at baseline for age, NYHA class, gender, peak VO2 and medication use (Table 1). Five studies utilised daily training, two studies required patients to train 6 days weekly and four studies required patients to train thrice weekly. Four studies required patients to

Discussion

The present meta-analysis of 11 studies of IMT vs. Control (sham IMT or sedentary) included nearly 300 CHF patients. The major finding is that all primary and secondary outcome measures showed a significant improvement with IMT training. The effect size of the primary outcome measure was comparable with changes in peak VO2 reported in previous meta-analyses of conventional aerobic exercise training [20].

Our analyses suggested two measures of cardio-respiratory fitness, peak VO2 and 6MWD are

Conclusion

Respiratory muscle training improves cardio-respiratory fitness and quality of life to a similar magnitude as conventional exercise training. Respiratory muscle training may provide an initial alternative to the more severely de-conditioned heart failure patients who may then transition to conventional exercise training.

Acknowledgements

The authors wish to thank Lisa Gurney for conducting a systematic search of the literature. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.

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