Inspiratory muscle training during rehabilitation in successfully weaned hypercapnic patients with COPD

Abstract

Background: This study is aimed to evaluate the effect of inspiratory muscle training (IMT) added to rehabilitation in patients with chronic obstructive pulmonary disease (COPD) who remain hypercapnic and use non-invasive ventilation after successful weaning.

Methods: Patients received rehabilitation and were randomized to inspiratory muscle or sham training for 4 weeks. The primary outcome was distance walked within 6 min. Secondary outcomes were inspiratory muscle strength, endurance, lung function, and blood gas levels.

Results: Twenty-nine patients participated in this study. Walking distance of the sham group increased from 93 ± 52 m at baseline to 196 ± 85 m at week 4 (p = 0.019, 95% CI: 11-196 m). Patients in the IMT group significantly improved their walking distance from 94 ± 32 to 290 ± 75 m (p < 0.0001 [107-286 m]; p = 0.04 [3-186 m] for between-group comparison). Patients in the IMT group increased their maximal inspiratory pressure from -35 ± 8 to -55 ± 11 cmH₂O (p = 0.001; -6 to -33 cmH₂O), while the increase in the sham group failed to reach significance (-29 ± 10 to -37 ± 13 cmH₂O [-22 to 6 cmH₂O]). Inspiratory power increased from 9.6 ± 5.4 to 20.7 ± 9.7 joules/min (2.6-19.5 joules/min, p = 0.003) in the IMT group, while no significant change occurred in the sham group (7.6 ± 4.2 joules/min at study entry and 11.1 ± 6.9 joules/min [-5.2-12.3 joules/min] at study end).

Conclusions: Rehabilitation of successfully weaned patients with COPD and persistent hypercapnia significantly improves functional exercise capacity. Additional IMT significantly enhances functional exercise capacity and increases respiratory muscle strength and power.

Keywords: COPD pathology; Non-invasive ventilation; Pulmonary rehabilitation; Respiratory muscles.