The chronic obstructive pulmonary disease (COPD) is characterized by chronic obstruction to airflow, which leads to respiratory muscle overload and greater activation of accessory muscles of respiration, especially those active in the inspiratory phase. It is believed that the positive expiratory pressure (EPAP) reduces respiratory work, producing less activation of these muscles. Thus, we evaluate the behavior of the electrical activity of inspiratory muscles of COPD patients in response to application of expiratory positive airway pressure (EPAP), and to observe the influence of pressure level in inspiratory muscle recruitment. This will be implemented for a clinical single blinded trial (blinded to gauge the outcome) developed in the Department of Pneumology, Hospital de Clinicas de Porto Alegre (HCPA). Will be evaluated in COPD patients with a clinical diagnosis of pathology, and of both genders and should be aged between 40 and 70 years. In a first day will be collected anthropometric data, performed the lung function test for the staging of pathology and muscle strength testing. These same individuals will return to evaluate the electromyographic activity of sternocleidomastoid (SCM), and parasternal, both from the right hemisphere. This evaluation will consist in the measurement during breathing at rest (control), with the implementation of EPAP mask 10 or 15 cmH2O (state intervention) and 10 minutes after its removal. To test the lung function will be assessed using a spirometer and the lung capacity compared to the predicted in literature. As the electrical activity of muscle, will be observed the percentage of activation obtained for the highest activity (% RMS). Thus, it is expected that the implementation of EPAP promotes reduction of the electrical activity of muscle ECM and leverage the action of the parasternal muscle, affected by dynamic hyperinflation. It is also hoped that the use of blood pressure level of 15 cmH2O, compared to 10 cmH2O, the leverage effect of EPAP on the muscles of interest. The surface electromyographic evaluation is a method of relatively inexpensive and noninvasive, and is effective in evaluating the electrical potential that lies on the muscle membrane. So, will describe the effect of EPAP on the inspiratory muscles, which will be important to guide treatment of COPD patients using positive airway pressure therapy.