 The purpose of this study is to evaluate the safety and efficacy of four times daily oscillatory Positive Expiratory Pressure oPEP Aerobika use over 4 weeks in individuals with stable chronic obstructive pulmonary disease COPD. The investigators hypothesize that daily oPEP use will significantly improve St. Georges Respiratory Questionnaire SGRQ score, six-minute walk distance 6MWD and forced expiratory volume in one second FEV1 after four weeks of four times daily administration. 