Chronic obstructive pulmonary disease (COPD) is a widespread medical condition. COPD is leading in morbidity and mortality worldwide. The sputum samples from COPD patients were investigated microbiologically. The oxygen partial pressure in sputum was measured. In all sputum specimens obligate anaerobes were detected. Bacterial number scameto 1,8x107± 4,5x107cfu/ml. Compared to patients with COPD level III, obligate anaerobic bacteria were reduced significantly in patients with COPD level IV. The pO2was reduced compared. There duced numbers of obligate anaerobes from patients with COPD level IV maybe interpreted as a consequence of non-invasive ventilation therapies using pure oxygen. Possibly, an early non-invasive ventilation of COPD patients level III with pure oxygen may reduce the high quantities of obligate anaerobes in sputum of these patients and, thus, may constitute a new therapeutic option for COPD patients.