Acute Effects of Incremental Inspiratory Loads on Respiratory Mechanics and NRD in Patient With Stable COPD.

The patients with COPD will be admitted in one intervention groups(performing on threshold loading device).Before using threshold loading device, we will measure the relevant parameters of lung volume, respiratory flow,diaphragm electromyogram, central drive mechanical and other baseline index.Then incremental inspiratory load will be applied to investigate the effects of inspiratory load on the above mentioned respiratory mechanics parameters.