Effects of inspiratory muscle training on cardiovascular autonomic functions in patients with COPD

<bold>Background:</bold> Heart rate variability (HRV) is known to be altered in patients with COPD exhibiting inspiratory muscle weakness, resulting in enhanced sympathetic and decreased parasympathetic activities. Inspiratory muscle training (IMT), a specific regimen targeting inspiratory muscles, has shown efficacy in improving inspiratory muscle strength (PImax). However, the effects of 8-week the highest tolerable intensity IMT on HRV in these patients has not been studied. <bold>Aims:</bold> To compare HRV alterations between baseline and after 8 weeks in IMT and control group. <bold>Methods:</bold> A total of 27 patients with COPD were randomly assigned to either IMT (n=13) or control group (n=14). The IMT group underwent two daily sessions of 30 breaths, 7 days a week, for 8 weeks, with the highest tolerable intensity using tapered flow resistive device, while the control group received pharmacological treatment. PImax and short-term HRV assessments were performed at baseline and after 8 weeks. <bold>Results:</bold> The IMT group exhibited a significant increase in PImax after training (85±28.4 to 109±25.2 cmH2O; p<0.05). The low-frequency (LF) component of HRV significantly decreased (51.27±20.92 to 38.33±16.61 nu; p=0.002), while the high-frequency (HF) component significantly increased (39.61±19.64 to 47.91±17.24 nu; p=0.039). LF/HF ratio showed a significant decrease (2.29±2.76 to 1.09±0.94; p=0.044). No significant differences were observed in LF, HF, and LF/HF ratio in the control group. <bold>Conclusions:</bold> After 8 weeks of IMT, heart rate variability improved, characterized by decreased sympathetic and increased parasympathetic activities. These data support beneficial effect of IMT in patients with COPD.