Respiratory physiological mechanism of two types of equal-intensity inspiratory muscle training in stable patients with chronic obstructive pulmonary disease

Abstract

PurposeThis study aimed to investigate the respiratory physiological changes resulting from short-term inspiratory resistance training (R-IMT) and inspiratory threshold training (T-IMT) in patients with chronic obstructive pulmonary disease (COPD) and to compare the mechanisms of the two training methods. Patients and methodsA total of 75 stable patients with COPD combined with inspiratory muscle weakness were randomly allocated to three groups: R-IMT (n = 26), T-IMT (n = 24), and control (n = 25). Before and after 8 weeks of inspiratory muscle training(IMT), cardiopulmonary exercise tests were conducted to assess respiratory patterns, respiratory central drive, exercise tolerance, and ventilation efficiency. ResultsAfter 8 weeks of IMT, Inspiratory muscle strength, represented by MIP (maximum inspiratory mouth pressure) and exercise capacity increased during exercise in both IMT groups (P < 0.05). In the R-IMT group, inspiratory time (Ti) prolonged (P < 0.05), tidal volume (Vt) increased (P < 0.05), ventilation efficiency (represented by ventilation-center coupling) increased (P < 0.05) during exercise. Conversely, the T-IMT group did not exhibit any of these changes after IMT (P > 0.05). ConclusionIn summary, the improvement in exercise tolerance was associated with an increase in inspiratory muscle reserve in both R-IMT and T-IMT. However, only R-IMT was associated with deeper and slower breathing, as well as improved ventilation efficiency.