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

Purpose

This 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 methods

A 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.

Results

After 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).

Conclusion

In 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.