| Patients admitted to the ICU without COPD | Patients admitted to the ICU because of acute respiratory failure due to COPD | Patients admitted to the ICU with comorbid COPD | p-value | |
| Subjects | 177 679 | 4868 | 11 906 | |
| Demographic characteristics | ||||
| Age years | 62.5±17.3 | 67.2±12.1 | 68.7±13.2 | <0.0001#,¶,+ |
| Male patients | 101 674 (57.4) | 3087 (63.5) | 7191 (60.5) | <0.0001#,¶,+ |
| Type of admission | ||||
| Medical | 83 991 (47.5) | 4868 (100.0) | 5131 (43.2) | <0.0001#,¶,+ |
| Scheduled surgical | 59 604 (33.7) | 0 (0.0) | 4023 (33.8) | <0.0001#,+ |
| Unscheduled surgical | 33 177 (18.8) | 0 (0.0) | 2734 (23.0) | <0.0001#,¶,+ |
| Risk upon ICU admission | ||||
| SAPS II original model | 27.0 (18.0–40.0) | 41.0 (31.0–55.0) | 34.0 (24.0–48.0) | <0.0001#,¶,+ |
| SAPS II predicted mortality | 34 202 (19.3) | 1746 (35.9) | 3201 (26.9) | <0.0001#,¶,+ |
| Outcome | ||||
| ICU length of stay days | 3.00 (2.00–6.00) | 6.00 (3.00–14.00) | 4.00 (2.00–9.00) | <0.0001#,¶,+ |
| Observed ICU mortality | 18 907 (10.6) | 1017 (20.9) | 2127 (17.9) | <0.0001#,¶,+ |
| Post-ICU mortality | 8599 (4.8) | 532 (10.9) | 1007 (8.5) | <0.0001#,¶,+ |
| Observed hospital mortality | 27 520 (15.5) | 1549 (31.8) | 3134 (26.3) | <0.0001#,¶,+ |
| Ratio of observed to expected mortality (95% CI) | 0.805 (0.797–0.812) | 0.887 (0.857–0.918) | 0.979 (0.956–1.003) | |
| Patients with prolonged mechanical ventilation | 22 961 (12.9) | 1675 (34.4) | 2406 (20.2) | <0.0001#,¶,+ |
| Patients requiring tracheotomy | 10 516 (5.9) | 966 (19.8) | 1424 (12.0) | <0.0001#,¶,+ |
| Patients with prolonged weaning | 4140 (2.3) | 452 (9.3) | 462 (3.9) | <0.0001#,¶,+ |
Data are presented as n, mean±sd, n (%) or median (interquartile range), unless otherwise stated. SAPS: Simplified Acute Physiology Score. p-values for comorbidites and diagnoses at admission obtained by Chi-squared test and for outcome obtained by Mann–Whitney U-test. #: significant difference between patients without COPD versus patients admitted to the ICU because of acute respiratory failure due to COPD in post hoc analysis; ¶: significant difference between patients without COPD versus patients with comorbid COPD in post hoc analysis; +: significant difference between patients admitted to the ICU because of acute respiratory failure due to COPD versus patients with comorbid COPD in post hoc analysis.