 We will carefully select COPD patients ready for discharge from an acute care hospital and will be invited to participate in this trial. Participants will then undergo a run-in phase of 4 weeks during which their clinical status will be stabilized. Patients experiencing a clinical exacerbation during the run-in phase will be excluded from the study. After the run-in phase, patients will be randomly assigned to one of two groups: nocturnal NIMV therapy standard medical therapy or sham standard medical therapy. The Chronic Respiratory Questionnaire CRQ and the Health Utilities Index Mark 23 HUI 2 and HUI 3 will be used to measure HRQL of study participants at baseline and then at 2, 4, 6, 8, 10 and 12 weeks. We will also measure the study participants exacerbation rate during the study period. A six-minute walk test will be used to determine the walking capacity of the study participants. In addition, 2-D echocardiography and 24-hour ambulatory electrocardiographic monitoring will be used to determine the effect of nocturnal NIMV on cardiac performance over a 3 month period. Finally, we will perform a comprehensive economic analysis to determine the costs as well as the benefits associated with the nocturnal NIMV therapy. 