Table 1 Demographic characteristics
| Â | Training cohort | pa | Validation cohort | pa | pb | ||
|---|---|---|---|---|---|---|---|
NIV success N = 922 | NIV failure N = 529 | NIV success N = 400 | NIV failure N = 328 | ||||
Age, years | 63 ± 16 | 64 ± 16 | 0.61 | 61 ± 17 | 61 ± 16 | 0.99 |  < 0.01 |
Male | 593 (64.3%) | 377 (71.3%) |  < 0.01 | 273 (68.3%) | 217 (66.2%) | 0.58 | 0.85 |
SOFA score | 4.6 ± 2.4 | 6.1 ± 3.0 |  < 0.01 | 4.9 ± 2.1 | 6.0 ± 2.8 |  < 0.01 | 0.03 |
Septic shock | 67 (7.3%) | 138 (26.1%) |  < 0.01 | 14 (3.5%) | 59 (18.0%) |  < 0.01 |  < 0.01 |
Presence of COVID-19 | 4 (0.4%) | 0 (0%) | 0.30 | 17 (4.3%) | 26 (7.9%) | 0.04 |  < 0.01 |
ICU type | |||||||
 Medical | 450 (48.8%) | 300 (56.7%) |  < 0.01 | 179 (44.8%) | 151 (46.0%) | 0.77 | 0.19 |
 Surgical | 145 (15.7%) | 58 (11.0%) | 0.01 | 58 (14.5%) | 50 (15.2%) | 0.83 | 0.60 |
 Mixed | 327 (35.5%) | 171 (32.3%) | 0.23 | 163 (40.8%) | 127 (38.7%) | 0.60 | 0.01 |
Reason for NIV | |||||||
 Pneumonia | 363 (39.4%) | 347 (65.6%) |  < 0.01 | 230 (57.5%) | 255 (77.7%) |  < 0.01 |  < 0.01 |
 Nonpulmonary sepsis | 113 (12.3%) | 79 (14.9%) | 0.15 | 29 (7.3%) | 27 (8.2%) | 0.68 |  < 0.01 |
 Pancreatitis | 109 (11.8%) | 32 (6.0%) |  < 0.01 | 23 (5.8%) | 8 (2.4%) | 0.04 |  < 0.01 |
 CPE | 131 (14.2%) | 7 (1.3%) |  < 0.01 | 40 (10.0%) | 4 (1.2%) |  < 0.01 |  < 0.01 |
 Cardiac problem other than CPE | 58 (6.3%) | 16 (3.0%) |  < 0.01 | 11 (2.8%) | 10 (3.0%) | 0.83 | 0.02 |
 Pulmonary embolism | 16 (1.7%) | 10 (1.9%) | 0.84 | 8 (2.0%) | 3 (0.9%) | 0.36 | 0.73 |
 Trauma | 19 (2.1%) | 5 (0.9%) | 0.14 | 13 (3.3%) | 5 (1.5%) | 0.16 | 0.19 |
 Poison | 8 (0.9%) | 5 (0.9%) |  > 0.99 | 3 (0.8%) | 0 (0%) | 0.26 | 0.29 |
 Postoperative respiratory failure | 9 (1.0%) | 3 (0.6%) | 0.55 | 9 (2.3%) | 3 (0.9%) | 0.24 | 0.13 |
 Asthma | 7 (0.8%) | 0 (0%) | 0.05 | 1 (0.3%) | 0 (0%) |  > 0.99 | 0.28 |
 Inhalation injury | 4 (0.4%) | 0 (0%) | 0.30 | 1 (0.3%) | 1 (0.3%) |  > 0.99 |  > 0.99 |
 Other | 85 (9.2%) | 25 (4.7%) |  < 0.01 | 32 (8.0%) | 12 (3.7%) | 0.02 | 0.22 |
Presence of ARDS | |||||||
 Pulmonary ARDS | 49 (5.3%) | 102 (19.3%) |  < 0.01 | 48 (12.0%) | 78 (23.8%) |  < 0.01 |  < 0.01 |
Extrapulmonary  ARDS | 109 (11.8%) | 51 (9.6%) | 0.22 | 9 (2.3%) | 8 (2.4%) |  > 0.99 |  < 0.01 |
Underlying disease | |||||||
 Hypertension | 394 (42.7%) | 193 (36.5%) | 0.02 | 166 (41.5%) | 102 (31.3%) |  < 0.01 | 0.10 |
 Diabetes mellitus | 261 (28.3%) | 130 (24.6%) | 0.13 | 91 (22.8%) | 68 (20.7%) | 0.53 | 0.01 |
 Chronic kidney disease | 109 (11.8%) | 41 (7.8%) | 0.02 | 73 (18.3%) | 41 (14.5%) | 0.04 |  < 0.01 |
 Chronic liver disease | 24 (2.6%) | 22 (4.2%) | 0.12 | 21 (5.3%) | 23 (7.0%) | 0.35 |  < 0.01 |
 Chronic heart disease | 300 (32.5%) | 109 (20.6%) |  < 0.01 | 119 (29.8%) | 84 (25.6%) | 0.25 | 0.92 |
 Chronic lung disease | 143 (15.5%) | 69 (13.0%) | 0.22 | 60 (15.0%) | 40 (12.2%) | 0.28 | 0.60 |
 Presence of immunosuppression | 45 (4.9%) | 72 (13.6%) |  < 0.01 | 60 (15.0%) | 81 (24.7%) |  < 0.01 |  < 0.01 |
Variables collected before NIV | |||||||
 GCS | 14.8 ± 0.6 | 14.6 ± 1.0 |  < 0.01 | 14.4 ± 1.5 | 14.2 ± 2.2 | 0.07 |  < 0.01 |
 Heart rate, beats/min | 114 ± 24 | 118 ± 24 |  < 0.01 | 106 ± 23 | 111 ± 23 |  < 0.01 |  < 0.01 |
 Respiratory rate, breaths/min | 30 ± 7 | 33 ± 8 |  < 0.01 | 28 ± 6 | 30 ± 8 |  < 0.01 |  < 0.01 |
 Systolic blood pressure, mmHg | 134 ± 27 | 129 ± 26 |  < 0.01 | 134 ± 24 | 128 ± 25 |  < 0.01 | 0.49 |
 Diastolic blood pressure, mmHg | 78 ± 17 | 75 ± 17 | 0.02 | 78 ± 17 | 74 ± 15 |  < 0.01 | 0.52 |
 pH | 7.42 ± 0.10 | 7.41 ± 0.12 | 0.11 | 7.43 ± 0.08 | 7.42 ± 0.10 | 0.04 | 0.11 |
 PaCO2, mmHg | 33 ± 8 | 32 ± 8 | 0.01 | 34 ± 7 | 34 ± 8 | 0.67 |  < 0.01 |
 PaO2/FiO2, mmHg | 178 ± 74 | 153 ± 60 |  < 0.01 | 147 ± 104 | 137 ± 85 | 0.16 |  < 0.01 |
 HACOR score | 4.7 ± 2.7 | 6.4 ± 3.1 |  < 0.01 | 5.7 ± 3.1 | 6.9 ± 3.5 |  < 0.01 |  < 0.01 |
Variables collected after 1–2 h of NIV | |||||||
 GCS | 14.9 ± 0.4 | 14.5 ± 1.2 |  < 0.01 | 14.5 ± 1.5 | 14.2 ± 2.2 | 0.03 |  < 0.01 |
 Heart rate, beats/min | 105 ± 22 | 112 ± 24 |  < 0.01 | 100 ± 21 | 107 ± 22 |  < 0.01 |  < 0.01 |
 Respiratory rate, breaths/min | 26 ± 6 | 31 ± 8 |  < 0.01 | 25 ± 6 | 28 ± 8 |  < 0.01 |  < 0.01 |
 Systolic blood pressure, mmHg | 129 ± 23 | 127 ± 25 | 0.19 | 128 ± 22 | 124 ± 22 | 0.01 | 0.05 |
 Diastolic blood pressure, mmHg | 73 ± 14 | 71 ± 16 | 0.06 | 76 ± 15 | 73 ± 14 | 0.01 |  < 0.01 |
 pH | 7.44 ± 0.07 | 7.40 ± 0.11 |  < 0.01 | 7.44 ± 0.06 | 7.42 ± 0.09 | 0.01 | 0.22 |
 PaCO2, mmHg | 34 ± 7 | 34 ± 12 | 0.38 | 35 ± 7 | 35 ± 9 | 0.70 | 0.03 |
 PaO2/FiO2, mmHg | 241 ± 108 | 168 ± 89 |  < 0.01 | 182 ± 67 | 140 ± 61 |  < 0.01 |  < 0.01 |
 HACOR score | 2.5 ± 2.2 | 6.0 ± 3.6 |  < 0.01 | 3.9 ± 2.9 | 6.2 ± 3.5 |  < 0.01 |  < 0.01 |
De novo acute respiratory failure | 508 (55.1%) | 358 (69.6%) |  < 0.01 | 233 (58.3%) | 215 (65.5%) |  < 0.05 | 0.93 |
Outcome | |||||||
 Death in hospital | 53 (5.7%) | 256 (48.4%) |  < 0.01 | 15 (3.8%) | 153 (46.6%) |  < 0.01 | 0.35 |
 Length of ICU stay, days | 6 (4–10) | 7 (3–13) | 0.14 | 7 (5–12) | 9 (4–16) | 0.20 |  < 0.01 |
 Length of hospital stay, days | 16 (10–26) | 11 (5–22) |  < 0.01 | 18 (11–28) | 14 (6–24) |  < 0.01 | 0.02 |