| Patients admitted to the ICU without COPD | Patients admitted to the ICU because of ARF due to COPD | Patients admitted to the ICU with comorbid COPD | p-value | |
| Subjects | 177 679 | 4868 | 11 906 | |
| Comorbidities | ||||
| None | 120 009 (67.5) | 983 (20.2) | 362 (3.0) | <0.0001#,¶,+ |
| Haematological disease | 1957 (1.1) | 54 (1.1) | 222 (1.9) | <0.0001¶,+ |
| AIDS | 256 (0.1) | 13 (0.3) | 10 (0.1) | 0.0171+ |
| Metastasising malignancy | 6722 (3.8) | 139 (2.9) | 671 (5.6) | <0.0001#,¶,+ |
| Immunosuppression | 2267 (1.3) | 142 (2.9) | 444 (3.7) | <0.0001#,¶,+ |
| Chronic renal failure | 10 180 (5.7) | 489 (10.1) | 2025 (17.0) | <0.0001#,¶,+ |
| Chronic respiratory failure | 0 (0.0) | 3539 (72.7) | 11 335 (95.2) | <0.0001#,¶,+ |
| Chronic heart failure | 19 354 (10.9) | 1039 (21.3) | 4248 (35.7) | <0.0001#,¶,+ |
| Liver cirrhosis | 4390 (2.5) | 145 (3.0) | 516 (4.3) | <0.0001#,¶,+ |
| Alcoholism | 7796 (4.4) | 413 (8.5) | 868 (7.3) | <0.0001#,¶,+ |
| Insulin-dependent diabetes | 8035 (4.5) | 348 (7.2) | 1049 (8.8) | <0.0001#,¶,+ |
| Acute renal failure | 4066 (2.3) | 147 (3.0) | 728 (6.1) | <0.0001#,¶,+ |
| Non-metastasising malignancy | 10 617 (6.0) | 223 (4.6) | 1201 (10.1) | <0.0001#,¶,+ |
| Drug addiction | 2251 (1.3) | 43 (0.9) | 64 (0.5) | <0.0001#,¶ |
| Main cause of ICU admission | ||||
| Medical cause | ||||
| Cardiovascular disease | 32 234 (20.9) | 0 | 2011 (19.0) | <0.0001#,¶,+ |
| Respiratory disease | 8034 (5.2) | 4868 (100.0) | 929 (8.8) | <0.0001#,¶,+ |
| Renal disease | 2425 (1.6) | 0 | 324 (3.1) | <0.0001#,¶,+ |
| Metabolic disease | 7786 (5.1) | 0 | 121 (1.1) | <0.0001#,¶,+ |
| Gastrointestinal disease | 3129 (2.0) | 0 | 215 (2.0) | <0.0001#,+ |
| Haematological disease | 256 (0.2) | 0 | 14 (0.1) | 0.0129# |
| Shock | 3428 (2.2) | 0 | 422 (4.0) | <0.0001#,¶,+ |
| Sepsis | 2251 (1.5) | 0 | 259 (2.5) | <0.0001#,¶,+ |
| Neurological disease | 6326 (4.1) | 0 | 361 (3.4) | <0.0001#,¶,+ |
| Trauma (not operated) | 3569 (2.3) | 0 | 139 (1.3) | <0.0001#,¶,+ |
| Medical, not otherwise specified | 1502 (1.0) | 0 | 42 (0.4) | <0.0001#,¶,+ |
| Pregnancy | 177 (0.1) | 0 | 1 (0.0) | 0.0004¶ |
| Surgical cause | ||||
| Cardiovascular surgery | 18 781 (12.2) | 0 | 1135 (10.7) | <0.0001#,¶,+ |
| Thoracic surgery | 1652 (1.1) | 0 | 278 (2.6) | <0.0001#,¶,+ |
| Abdominal surgery | 17 992 (11.7) | 0 | 1691 (16.0) | <0.0001#,¶,+ |
| Neurosurgery | 5909 (3.8) | 0 | 161 (1.5) | <0.0001#,¶,+ |
| Transplant surgery | 768 (0.5) | 0 | 218 (2.1) | <0.0001#,¶,+ |
| Trauma surgery | 19 154 (12.4) | 0 | 1078 (10.2) | <0.0001#,¶,+ |
| Surgery, not otherwise specified | 18 757 (12.2) | 0 | 1169 (11.1) | <0.0001#,¶,+ |
| Cause missing | 23 549 | 0 | 1338 | |
Data are presented as n or n (%), unless otherwise stated. p-values obtained by Chi-squared test. ARF: acute respiratory failure. #: 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.