The most significant pathophysiology change of COPD patients is persistent incompletely reversible airflow obstruction and increased lung volume. As a result, the work of breathing (WB) and neural respiratory drive (NRD) increased. Noninvasive positive pressure ventilation (NPPV) is the first-line treatment in acute exacerbation of COPD (AECOPD). One of the mechanisms is to reduce the load of respiratory muscles. It has been reported that NRD decreased in response to increase of pressure support. Detection of NRD can be the index of monitoring for titration of optimal level of ventilator support in the future.