Moderate-to-high intensity inspiratory muscle training improves the effects of combined training on exercise capacity in patients after coronary artery bypass graft surgery: A randomized clinical trial

Abstract

Background: The effects of adding moderate-to-high intensity inspiratory muscle training (IMT) to short-term aerobic and resistance exercise (combined training [CT]), after coronary artery bypass grafting (CABG) are not established. This study aimed to determine the effects of moderate-to-high intensity IMT + CT on exercise capacity, respiratory muscle strength, inspiratory muscle endurance, quality of life (QoL), and laboratory biomarkers in patients after CABG who were participants of a phase II cardiac rehabilitation program.

Methods: Twenty-four patients were randomly assigned to either the IMT + CT group (n = 12), who performed moderate-to-high intensity IMT with CT or the sham-IMT + CT group (n = 12). Patients completed two sessions per week for 12 weeks. Each patient underwent a cardiopulmonary exercise test, six-minute walk test (6MWT), respiratory muscle strength and endurance evaluation, QoL questionnaire, and serum advanced oxidation protein products, ferric reducing antioxidant power [FRAP], nitrate/nitrate, and high-sensitivity C-reactive protein, before and after the 12-week intervention.

Results: The IMT + CT group showed significantly greater improvements in peak oxygen uptake (1.3 mL∙kg^-1∙min^-1; 95% confidence interval [95% CI], 0.5 to 2.2), distance covered during the 6MWT (78.8 m; 95% CI, 28.1 to 129.5), maximal inspiratory pressure (23.0 cmH₂O; 95% CI, 9.3 to 36.7), QoL (-15.1 points; 95% CI, -26.9 to -3.3), and FRAP (83.7 μmol/L; 95% CI, 20.2 to 147.1) compared to the sham-IMT + CT group as a result of the intervention.

Conclusions: Short-term moderate-to-high intensity IMT with CT provided additional benefits in exercise capacity, inspiratory muscle strength, QoL, and antioxidant profile in patients after CABG. Trial Registration clinicaltrials.gov Identifier: NCT02885077.

Keywords: Combined training; Coronary artery bypass grafting; Functional capacity; Inspiratory muscle training; Respiratory function.