The impact of high-intensity inspiratory muscle training on exercise capacity and inspiratory muscle strength in heart failure with reduced ejection fraction: a systematic review and meta-analysis

Objective:: Inspiratory muscle training (IMT) improves prognostic clinical variables in patients with heart failure. However, the optimal intensity for increasing those outcomes remains unclear. Thus, we aimed to determine whether high-intensity inspiratory muscle training (HIIMT) improves exercise capacity and respiratory muscle strength in patients with heart failure with reduced ejection fraction (HFrEF).

Methods:: We searched for randomized controlled clinical trials at MEDLINE, the Cochrane Central Register of Controlled Trials, the Physiotherapy Evidence Database, SciELO and CINAHL from the earliest date available to May 2018. Primary studies on HIIMT against low-intensity IMT or sham-IMT that evaluated exercise capacity and inspiratory muscle strength were included. Two independent reviewers evaluated the eligibility of studies retrieved from the databases. Disagreements were resolved by discussion or by a third reviewer. Weighted mean difference (WMD), standardized mean difference (SMD) and 95% confidence interval (CI) were estimated by random effect models.

Results:: Five studies met the eligibility criteria (138 patients). HIIMT improved VO₂peak (WMD 2.65 mL kg^-1 min^-1; 95% CI: 2.2 to 3.1 mL kg^-1 min^-1), walking tests (SMD 1.71; 95% CI: 0.83 to 2.59) and maximal inspiratory pressure (WMD 16.63 cmH₂O; 95% CI: 10.34 to 22.91 cmH₂O). The estimate for potential risks of adverse events was not performed because of the low prevalence of reports in primary studies.

Conclusion:: HIIMT seems to be a useful strategy for improving exercise capacity and inspiratory muscle strength in HFrEF patients.