The Effect of Different Respiratory Muscle Training Protocols on Health Outcomes in Patients with COPD

Abstract

PURPOSE: Inspiratory muscle training (IMT) has been shown to improve dyspnoea, exercise tolerance and respiratory muscle strength in patients with chronic obstructive pulmonary disease (COPD), however the efficacy of expiratory muscle training (EMT) is equivocal. Respiratory muscle training (RMT) protocols are strenuous, therefore the purpose was to determine the effects of a modified IMT protocol or EMT protocol compared to standard IMT on respiratory health outcomes in patients with COPD. METHODS: 11 COPD patients enrolled in pulmonary rehabilitation completed a randomised controlled pilot trial involving either: eight breaths of IMT (IMT8), 30 breaths of IMT (IMT30) or 30 breaths of EMT (EMT30). RMT was performed twice daily, six days a week for six weeks, commencing at 25% of respiratory muscle strength and progressing by 5% per week up to 50% in the final week. Maximal inspiratory (PImax) and expiratory (PEmax) mouth pressures, Body mass index, airway Obstruction (FEV1), Dyspnoea (modified MRC scale) and Exercise capacity (6 minute walk test; 6MWD), for the calculation of BODE index, and anxiety and depression (hospital anxiety and depression scale; HADS) were recorded before and after the intervention. Data are presented as mean difference ± SD and percentage change while Cohen’s d were applied to determine small (≥0.2), moderate (≥0.5) and large (≥0.8) effect sizes. RESULTS: BODE index decreased in all groups (IMT8: 22% [d = -1.00], IMT30: 7% [d = -0.25] & EMT30: 36.5% [d = -1.08]), with IMT8 (-1.3 ± 1.3) and EMT30 (-1.3 ± 1.2) being the most meaningful. IMT8 & EMT30 were more effective in improving BODE index (d = 0.75 & d = 0.87, respectively) and reducing anxiety (d = -0.83 and d = -0.95, respectively) compared to IMT30. 6MWD increased in all groups: 17% in IMT8 (d = 0.85), 22% in IMT30 (d = 0.38) and 32% in EMT30 (d = 0.75). Both PImax (+15.4 ± 13.1 [d = 1.04] & 11.3 ± 21.4 cmH2O [d = 0.94] and PEmax (+4.0 ± 16.2 [d = 0.16] & 4.0 ± 13.5 cmH2O [d = 0.22]) increased following IMT8 and IMT30, respectively, whereas EMT30 had no positive effect on PImax/PEmax. Compliance was greater during IMT8 (98±2%) compared to IMT30 (85±14%; d = 1.33) and EMT30 (65±31%; d = 1.83). CONCLUSION: Both IMT protocols demonstrated similar improvements in respiratory muscle strength, however only IMT8 and EMT30 showed meaningful reductions in BODE index and HADS.