Exercise training increases respiratory muscle strength and exercise capacity in patients with chronic obstructive pulmonary disease and respiratory muscle weakness

Background: How respiratory muscle strength influences the effectiveness of pulmonary rehabilitation (PR) in patients with chronic obstructive pulmonary disease (COPD) is unclear. Objective: To investigate the benefits of PR in subjects with COPD according to respiratory muscle strength. Methods: Ninety-seven subjects with COPD were evaluated using maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), pulmonary function tests, the cardiopulmonary exercise test (CPET), and the St. George's Respiratory Questionnaire (SGRQ). Subjects were divided into four groups: 1 (normal MIP and MEP); 2 (low MIP); 3 (low MEP); and 4 (low MIP and MEP). Subjects underwent PR for 3 months; MIP, MEP, SGRQ and CPET were evaluated post-PR. Results: Subjects with both poor MIP and MEP had the highest dyspnea score, lowest exercise capacity, and poorest health-related quality of life (HRQoL). PR improved exercise capacity and HRQoL in all groups, with more improvement in MIP, MEP, tidal volume (on exercise), and dyspnea (at rest) in subjects with both low MIP and MEP. Conclusions: Patients with respiratory muscle weakness had worse dyspnea, lower exercise capacity, and poorer HRQoL at baseline. Exercise training improved respiratory muscle strength with concurrent improvement of exercise capacity, HRQoL, and dyspnea score. Subjects with both poor baseline MIP and MEP showed greater benefits of PR. (C) 2020 Elsevier Inc. All rights reserved.