Effects of controlled inspiratory muscle training in patients with COPD: a meta-analysis

The purpose of this meta-analysis is to review studies investigating the efficacy of inspiratory muscle training (IMT) in chronic obstructive pulmonary disease (COPD) patients and to find out whether patient characteristics influence the efficacy of IMT. A systematic literature search was performed using the Medline and Embase databases. On the basis of a methodological framework, a critical review was performed and summary effect-sizes were calculated by applying fixed and random effects models. Both IMT alone and IMT as adjunct to general exercise reconditioning significantly increased inspiratory muscle strength and endurance. A significant effect was found for dyspnoea at rest and during exercise. Improved functional exercise capacity tended to be an additional effect of IMT alone and as an adjunct to general exercise reconditioning, but this trend did not reach statistical significance. No significant correlations were found for training effects with patient characteristics. However, subgroup analysis in IMT plus exercise training revealed that patients with inspiratory muscle weakness improved significantly more compared to patients without inspiratory muscle weakness. From this review it is concluded that inspiratory muscle training is an important addition to a pulmonary rehabilitation programme directed at chronic obstructive pulmonary disease patients with inspiratory muscle weakness. The effect on exercise performance is still to be determined.