Fig. (4) Survival probability of the different subgroups of patients with a prolonged weaning time of more than 4 weeks before they were admitted to our weaning unit over a time period of 18 months - 54 patients after surgery, 16 patients with COPD exacerbations, and 14 patients with different other reasons for prolonged weaning. Especially the post surgery patients had a worse outcome but this is statistically not significant because these patients were older and had more accompanying disease.