NRD can be measured with minute ventilation, inspiratory pressure change、mean inspiration flow and electromyography(EMG) of inspiratory muscles. However, the first three methods are subjected to the influenced of lung volume, airway resistance and compliance of respiratory system. So, electromyography is the most reliable measurement in evaluating NRD that can be used for human. Currently the standard method for evaluation of NRD with EMG is using esophageal multi-paired electrodes catheter ,since it is far away from chest wall and close to diaphragm , so the contamination from other respiratory muscles can be reduced .However, catheter placement into esophagus is necessary for this measurement, which limits its use in daily practice. Surface respiratory EMG is a noninvasive measurement. Although it subjected to contamination and less sensitive, recent advance in technology with multiple pair of surface electrodes, including surface diaphragm EMG、parasternal EMG and so on, it is possible to sufficient signals for evaluation of NRD. It has been the hot topics of research recently due to its noninvasive, easiness of use and appropriate for continuing monitor.