Background: About 10% of the patients with chronic obstructive pulmonary disease ( COPD) are at high risk for prolonged mechanical ventilation (MV >21 days), and mortality ranges from 55 to 78% in these patients. Objective: To determine the potential risk factors for MV over periods of 1, 2 and 3 weeks in patients with COPD. Patients and Method: The characteristics of patients during the stable period of their disease, on admission to the intensive care unit (ICU) and during the ICU stay were recorded prospectively and analyzed retrospectively for this study. t test, chi(2) test and logistic regression analysis were used for statistical analysis. Results: 86 patients with COPD requiring MV were included in the study. 73, 33, and 13% of the patients required MV longer than 1, 2 and 3 weeks, respectively. There were no significant relationships between the duration of MV and bronchiectasis or the presence of community-acquired pneumonia on admission, baseline pulmonary function test results or blood gas parameters on admission. Development of ventilator-associated pneumonia (VAP; odds ratio, OR: 6; 95% confidence interval, CI: 2 - 23, p = 0.011) and sepsis ( OR: 10; 95% CI: 2 - 54, p = 0.007) were independent predictors for MV >7 days. VAP was still a risk factor for MV > 15 days with an OR of 14 ( 95% CI: 3 - 66, p = 0.001). On the other hand MV > 21 days was primarily determined by increasing age ( OR: 1.2; 95% CI: 1 - 1.3, p = 0.042), severity of the disease on admission measured by APACHE II score ( OR: 1.4; 95% CI: 1 - 1.7, p = 0.002) and albumin levels ( OR: 0.10, 95% CI: 0.01 - 0.54, p = 0.007). Conclusion: Advanced age, severity of disease on admission and development of VAP during ICU stay are the main determinants of MV duration in patients with COPD. Copyright (C) 2005 S. Karger AG, Basel.