Analyse the Correlation Between sEMG and EMGdi

"before experiment ,every subject use a flanged mouthpiece attached to a manually operated occlusion valve in order to measure maximal inspiratory pressure (MIP)at functional residual capacity .~healthy subjects:increase the pressure in a water-sealed inspiratory threshold loading device in order to increase the neural respiratory drive.~COPD patients:increase the pressure in a non-invasive positive pressure ventilation in order to decrease the neural respiratory drive"