Risk factors for prone positioning(PP) in 2,409 patients who received endotracheal mechanical ventilation (MV) within 48 h after intensive care unit (ICU) admission, for ≥2 days, and who had arterial oxygen tension/inspiratory oxygen fraction (Pa,O2/FI,O2) ratios <300 during the first 48 h on MV
| Variables | SP | PP | p-value |
| Patients n | 2208 | 201 | |
| Age yrs | 66 (54–76) | 65 (50–75) | 0.04 |
| Males | 1411 (63.9) | 150 (74.6) | 0.002 |
| Transfer from ward | 1055 (47.8) | 112 (55.7) | 0.03 |
| Severity scores at admission | |||
| SAPS II | 52 (40–64) | 51 (40–65) | 0.85 |
| APACHE II score | 20 (15–25) | 20 (15–25) | 0.64 |
| SOFA score | 7 (5–10) | 7 (5–11) | 0.79 |
| Immunosuppression | |||
| Chemotherapy | 138 (6.3) | 10 (5) | 0.47 |
| Steroid therapy >1 month or >2 mg·kg−1 | 82 (3.7) | 11 (5.5) | 0.22 |
| AIDS | 45 (2) | 2 (1) | 0.31 |
| Bone marrow aplasia | 33 (1.5) | 4 (2) | 0.59 |
| Diagnosis at admission | |||
| Pneumonia | 450 (20.4) | 63 (31.3) | 0.0003 |
| Septic shock | 249 (11.3) | 31 (15.4) | 0.08 |
| Cardiac arrest | 181 (8.2) | 4 (2) | 0.002 |
| Acute respiratory failure | 130 (5.9) | 24 (11.9) | 0.001 |
| Stroke | 124 (5.6) | 7 (3.5) | 0.20 |
| Acute renal failure | 94 (4.3) | 3 (1.5) | 0.06 |
| COPD exacerbation | 78 (3.5) | 5 (2.5) | 0.44 |
| Cardiogenic pulmonary oedema | 66 (3) | 5 (2.5) | 0.69 |
| Multiple organ failure | 34 (1.5) | 7 (3.5) | 0.04 |
| Admission category# | |||
| Medical | 1562 (71) | 135 (67.5) | |
| Emergency surgery | 406 (18.4) | 36 (18) | 0.23 |
| Scheduled surgery | 233 (10.6) | 29 (14.5) | |
| Previous health status (McCabe) | |||
| Not fatal | 1267 (57.4) | 118 (58.7) | |
| Fatal within 5 yrs | 730 (33.1) | 69 (34.3) | 0.48 |
| Fatal within 1 yr | 211 (9.6) | 14 (7) | |
| Comorbidities¶ | |||
| Immunosuppression | 274 (12.4) | 29 (14.4) | 0.41 |
| Respiratory failure | 383 (17.3) | 42 (20.9) | 0.21 |
| Cardiovascular failure | 344 (15.6) | 26 (12.9) | 0.32 |
| Cirrhosis | 143 (6.5) | 21 (10.4) | 0.03 |
| Renal failure | 103 (4.7) | 9 (4.5) | 0.90 |
| At least one chronic disease | 962 (43.6) | 99 (49.3) | 0.12 |
| Main symptom at admission | |||
| Acute respiratory failure | 623 (28.2) | 71 (35.3) | 0.03 |
| Coma | 520 (23.6) | 17 (8.5) | <0.0001 |
| Septic shock | 407 (18.4) | 40 (19.9) | 0.61 |
| Multiple organ failure | 73 (3.3) | 11 (5.5) | 0.11 |
| Cardiogenic shock | 101 (4.6) | 6 (3) | 0.30 |
| Haemorrhagic shock | 89 (4) | 20 (10) | 0.0001 |
| Monitoring and scheduled surgery | 202 (9.1) | 15 (7.5) | 0.42 |
| COPD exacerbation | 53 (2.4) | 8 (4) | 0.17 |
| Acute renal failure | 34 (1.5) | 6 (3) | 0.12 |
| Trauma | 21 (1) | 3 (1.5) | 0.46 |
| Treatment during the first 48 h | |||
| Vasoactive drugs | 1413 (64) | 156 (77.6) | 0.0001 |
| Steroids | 680 (30.8) | 76 (37.8) | 0.04 |
| Antibiotics | 1753 (79.4) | 169 (84.1) | 0.11 |
| Enteral nutrition | 566 (25.6) | 35 (17.4) | 0.01 |
| Parenteral nutrition | 385 (17.4) | 45 (22.4) | 0.08 |
| Procedures during the first 48 h | |||
| Arterial catheter | 1119 (50.7) | 126 (62.7) | 0.001 |
| Central catheter | 1403 (63.5) | 162 (80.6) | 0.0001 |
| Swan catheter | 107 (4.8) | 20 (10) | 0.002 |
| At least one catheter | 1482 (67.1) | 170 (84.6) | <0.00014 |
| Laboratory variables in the first 48 h | |||
| Temperature max °C | 38.2 (37.7–38.9) | 38.6 (38–39.2) | <0.0001 |
| fC max bpm | 116 (100–135) | 126 (108–144) | <0.0001 |
| Prothrombin rate max % | 69 (55–80) | 61 (49–74) | <0.0001 |
| Lowest Pa,O2/FI,O2 ratio | 165.5 (112–220) | 129 (85–193) | <0.0001 |
| Laboratory variables in the first 48 h in categories | |||
| Temperature ≥38.2°C | 1146 (51.9) | 144 (71.6) | <0.0001 |
| fC ≥120 bpm | 1027 (46.5) | 128 (63.7) | <0.0001 |
| Prothrombin rate ≤65% | 917 (41.5) | 117 (58.2) | <0.0001 |
| Pa,O2/FI,O2 ratio | |||
| <100 | 436 (19.7) | 73 (36.3) | <0.0001 |
| 100–159 | 600 (27.2) | 57 (28.4) | |
| 160–219 | 614 (27.8) | 39 (19.4) | |
| 220–299 | 558 (25.3) | 32 (15.9) |
Data are presented as n (%) or median (interquartile range), unless otherwise stated. SP: supine position; SAPS II: Simplified Acute Physiology Score II; APACHE II: Acute Physiology and Chronic Health Evaluation II; SOFA: Sequential Organ Failure Assessment; COPD: chronic obstructive pulmonary disease; fC: cardiac frequency. #: data are missing for eight patients; ¶: evaluated using the APACHE II score (Knaus criteria). Variables within the first 48 h in the ICU were obtained as follows: in patients who received PP on the first ICU day, we only used the worst data collected on day 0; in patients who received MV on the second ICU day (day 1), we used the worst data collected on day 1; and in patients who received MV on the first ICU day (day 0), we used the worst data collected between day 0 and day 1.