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

backgroundInspiratory 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).  

objectivesTo 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

methodsWe 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

resultsWe 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 cmH AUTHORS'

conclusionsIMT 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.