Respiration failure type 2 is loss of the lungs ability to take up oxygen (O2) and get rid of carbon dioxide (CO2). The diagnosis is based on blood gas measurement of pressures of O2 and CO2. Patients with COPD is often seen to have co-morbidity with cardiac diseases. Chronic systemic inflammation is seen in both COPD and cardiac diseases. The investigators will investigate the sleep quality, CO2-retention, O2-saturation, cardiac arrythmias and markers of inflammation in 120 patients with COPD in different stages of the disease. Our hypotheses are:

• that the first signs of respiration failure type 2 is seen during sleep with alteration of sleep patterns and greater and more long-lasting retention of CO2 in the blood compared to those with a normal lung function
• that the use of alcohol, zopiclone or supplementary oxygen will make these differences even greater
• that cardiac arrythmias correlates with hypoxemia
• that cardiac arrythmias and respiration failure correlates with degree of inflammation

Inclusion Criteria:

• COPD (FEV1 < 80 % of pred. and FEV1/FVC < 0,7)

Exclusion Criteria:

• other serious disease (like lung cancer, sarcoidosis, restrictive lung disease)
• exacerbation of COPD within 3 weeks before inclusion
• coronary heart disease with unstable angina pectoris or myocardial infarction within 3 months of incl.
• uncontrolled hypertension
• cerebral infarction
• neurological, muscular or skeletal disease/disorder that affect abdominal- and/or thoracal movements (kyphoscoliosis, paresis, etc)
• unstable diabetes mellitus or signs of organ failure (anaemia, kidney failure, liver failure, etc)
• misuse/dependency of alcohol, sedatives, neurostimulating or narcotic drugs)
• obstructive sleep apnoea/hypopnoea syndrome
• using CPAP/BiPAP or home respirator
• pregnancy
• if PSG shows AHI > 30, or if patient becomes acutely ill between the nights with PSG, he/she will be withdrawn from the study