Changes in diaphragm thickness and 6-min walking distance improvement after inspiratory muscle training in patients with chronic obstructive pulmonary disease: Clinical trial.

AIM: Inspiratory muscle training (IMT) improves respiratory muscle function and exercise tolerance in patients with chronic obstructive pulmonary disease (COPD), but the detailed mechanism is unclear. The purpose of this study is to elucidate the mechanism of functional improvement by IMT from P0.1 , an index of respiratory central output, and thickness of diaphragm (Tdi), a noninvasive and reliable ultrasound examination.

METHODS: This clinical trial study enrolled 13 elderly patients with COPD. IMT was performed using the POWER breathe® Medic Plus breathing trainer in combination with each participant's outpatient rehabilitation regimen. Starting at 20% of the maximal inspiratory pressure (PImax) and increasing to 50%, the participants performed 30 IMT repetitions twice a day for 2 months. P0.1 is the value of airway-occlusion pressure at 0.1 s after the start of inspiratory flow, and Tdi was measured at rest and maximal breathing.

RESULTS: PImax and 6-min walking distance(6MWD) significantly increased after training. Tdi at resting inspiration and expiration, and maximal inspiration also significantly increased after training. In addition, the Borg Scale scores for dyspnea and leg fatigue and the respiratory rate of the 1-min recovery period after the 6MWD significantly decreased. There was no significant difference in P0.1 .

CONCLUSIONS: These results suggest that the effects of IMT may be attributed to the improved peripheral factors rather than to the central factors in elderly COPD patients.