Baseline characteristics of included patients
| Variable | Overall | Symptoms | p-value | |
| ≤14 days | >14 days | |||
| Patients n | 61 | 23 | 33 | 5 patients missing |
| Studies n | 76 | 32 | 38 | 6 studies missing |
| Age years | 66 (59–73) | 69 (60–76) | 65 (59–73) | 0.18 |
| Male | 55 (90) | 21 (91) | 30 (91) | 1 |
| BMI m·kg−2 | 28.5±4.9 | 28.1±4.9 | 28.6±5.2 | 0.75 |
| Mechanically ventilated | 58 (95) | 21 (98) | 32 (97) | 0.29 |
| Controlled ventilator mode | 35 (58) | 15 (65) | 15 (45) | 0.11 |
| NMBA use | 18 (30) | 7 (30) | 8 (24) | 0.84 |
| Days until LUS | ||||
| Symptoms | 15 (11–21) | 11 (9–13) | 20 (17–25) | N/A |
| Hospital admission | 7 (4–13) | 5 (3–6) | 13 (7–17) | 0.00 |
| ICU admission | 3 (1–12) | 2 (1–3) | 10 (3–19) | 0.00 |
| Mechanical ventilation | 4 (2–11) | 3 (1–4) | 10 (3–15) | 0.00 |
| Ventilator settings | ||||
| FIO2 % | 50 (40–60) | 55 (47–60) | 50 (40–60) | 0.49 |
| Pressure above PEEP cmH2O | 12 (10–15) | 13 (10–15) | 11 (5–17) | 0.17 |
| PEEP cmH2O | 12±3 | 12±4 | 11±3 | 0.05 |
| Arterial blood gas | ||||
| pH | 7.38 (7.33–7.45) | 7.37 (7.31–7.44) | 7.41 (7.34–7.45) | 0.19 |
| PaCO2 kPa | 6.6 (5.7–7.5) | 6.2 (5.6–7.2) | 6.7 (5.9–7.6) | 0.31 |
| PaO2 kPa | 9.7±1.3 | 9.8±1.4 | 9.6±1.2 | 0.55 |
| P/F ratio mmHg | 147±42 | 145±42 | 148±40 | 0.95 |
| Other | ||||
| SOFA | 8 (7–10) | 8 (7–10) | 9 (7–11) | 0.16 |
| Respiratory rate | 24±5 | 23±4 | 25±5 | 0.13 |
| Systolic blood pressure mmHg | 119 (106–132) | 117 (106–129) | 119 (107–138) | 0.71 |
| Diastolic blood pressure mmHg | 56 (51–63) | 55 (51–62) | 55 (50–64) | 0.85 |
| WBC ×109 cells·L−1 | 10.4 (6.6–15.2) | 8.7 (5.2–12.3) | 13.8 (7.8–17.7) | 0.01 |
| CRP mg·L−1 | 204±109 | 216±100 | 187±102 | 0.20 |
| Creatinine umol·L−1 | 96 (70–164) | 96 (70–150) | 99 (70–168) | 0.80 |
| Fluid balance since admission mL | 245 (−492–1027) | 344 (−442–835) | 215 (−904–1224) | 0.80 |
Data are presented as median (interquartile range), n (%) or mean±sd, unless otherwise stated. BMI: body mass index; NMBA: neuromuscular blockade; LUS: lung ultrasound score; ICU: intensive care unit; FIO2: inspiratory oxygen fraction; PEEP: positive end-expiratory pressure; PaCO2: arterial carbon dioxide tension; PaO2: arterial oxygen tension; P/F: PaO2/FIO2; SOFA: sequential organ failure assessment; WBC: white blood cell; CRP: C-reactive protein; N/A: not available.