Baseline characteristics of the patients
| Variable | Total population (N=895) | IMV (n=93) | Non-IMV (n=802) | P value |
| Age in years, mean (SD) | 67.0 (20.41) | 61.0 (19.90) | 67.8 (20.36) | 0.002 |
| Male gender, n (%) | 520 (58.1) | 61 (65.6) | 459 (57.2) | 0.122 |
| Comorbidities, n (%) | ||||
| HBP | 441 (49.3) | 43 (46.2) | 398 (49.6) | 0.536 |
| AMI | 63 (7.03) | 3 (3.22) | 56 (7.48) | 0.129 |
| COPD | 263 (29.4) | 24 (25.8) | 239 (29.8) | 0.423 |
| Clinical features, n (%) | ||||
| Cough | 733 (81.9) | 67 (72.0) | 666 (83.0) | 0.009 |
| Dyspnoea | 615 (68.7) | 71 (76.3) | 544 (67.8) | 0.094 |
| Fever | 421 (47.0) | 40 (43.0) | 381 (47.5) | 0.411 |
| Pleuritic pain | 221 (24.6) | 23 (24.7) | 198 (24.6) | 0.993 |
| Cyanosis | 81 (9.0) | 15 (16.1) | 66 (8.2) | 0.012 |
| Retractions | 178 (19.8) | 36 (38.7) | 142 (17.7) | <0.001 |
| Physical examination findings, mean (SD) | ||||
| Heart rate | 92.6 (19.91) | 100.6 (22.28) | 91.6 (19.41) | <0.001 |
| Systolic blood pressure | 119.6 (21.05) | 119.7 (27.17) | 119.6 (20.23) | 0.966 |
| Diastolic blood pressure | 70.5 (13.79) | 69.4 (15.21) | 70.7 (13.62) | 0.409 |
| Mean arterial pressure | 87.0 (14.87) | 86.2 (18.14) | 87.0 (14.44) | 0.685 |
| Respiratory rate | 21.7 (6.13) | 24.9 (8.90) | 21.4 (5.62) | <0.001 |
| Temperature | 37.0 (0.90) | 37.1 (1.05) | 37.0 (0.88) | 0.251 |
| SpO2 admission | 88.0 (7.25) | 86.3 (10.39) | 88.2 (6.77) | 0.080 |
| FiO2 admission | 27.8 (11.49) | 41.1 (22.37) | 25.9 (7.29) | <0.001 |
| Altered consciousness, n (%) | 149 (16.6) | 28 (30.1) | 121 (15.0) | <0.001 |
| Diagnostic imaging, n (%) | ||||
| Alveolar opacity on RX | 636 (71.4) | 64 (68.8) | 572 (71.7) | 0.551 |
| Consolidation on RX | 591 (66.4) | 54 (58.0) | 537 (67.3) | 0.072 |
| Multilobar pneumonia on RX | 245 (27.5) | 47 (50.5) | 198 (24.8) | <0.001 |
| Alveolar opacity on CT | 227 (67.3) | 29 (65.9) | 198 (67.5) | 0.826 |
| Consolidation on CT | 236 (70.0) | 33 (75.0) | 203 (69.2) | 0.440 |
| Multilobar pneumonia on CT | 137 (61.3) | 27 (61.3) | 110 (37.5) | 0.003 |
AMI, acute myocardial infarction; COPD, chronic obstructive pulmonary disease; FiO2, fraction of inspired oxygen; HBP, high blood pressure; IMV, invasive mechanically ventilated patients; non-IMV, non-invasive mechanically ventilated patients; RX, chest X-ray; SpO2, oxygen saturation by pulse oximetry.