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Table 4 Main characteristics of 456 patients with ARDS—classification 24 h after initial ARDS diagnosis based on SpO2/FiO2 cutoff of 190 and PEEP cutoff of 10 cm H2O

From: Risk stratification using SpO2/FiO2 and PEEP at initial ARDS diagnosis and after 24 h in patients with moderate or severe ARDS

Variables Group I (N = 213) Group II (N = 145) Group III (N = 17) Group IV (N = 81) P value
SpO2/FiO2 ≥ 190 and PEEP < 10 SpO2/FiO2 ≥ 190 and PEEP ≥ 10 SpO2/FiO2 < 190 and PEEP < 10 SpO2/FiO2 < 190 and PEEP ≥ 10
APACHE IV score 75 (60–93) 84 (65–108) 78 (65–112) 86 (68–110) 0.001
Age, years 63 (53–73) 60 (49–69) 57 (42–70) 59 (49–69) 0.018
Female 80 (37.6) 61 (42.1) 5 (29.4) 26 (32.1) 0.436
CCI 2 1 (0–3) 1 (0–2) 2 (0–3) 1 (0–2) 0.423
LIPS 8 (6.5–9.5) 9 (7.5–10.5) 7 (6.5–8) 9.5 (7.5–11.5) < 0.001
Tidal volume, ml/kg 6.4 (5.3–7.7) 6.2 (5.2–7.5) 7.2 (6.5–8.2) 6.4 (5.6–7.4) 0.166
FiO2, % 40 (36–40) 40 (40–50) 60 (55–60) 60 (55–65) < 0.001
PEEP, cm H2O 5 (5–8) 12 (10–13) 7 (5–8) 14 (12–15) < 0.001
Arterial pH 7.4 (7.4–7.5) 7.4 (7.3–7.4) 7.4 (7.3–7.5) 7.3 (7.3–7.4) < 0.001
PaCO2, kPa 5.3 (4.7–6.2) 5.6 (4.9–6.2) 5.6 (5–7) 5.8 (5.1–6.6) 0.018
Plasma lactate level, mmol/l 2.4 (1.4–4.1) 3.1 (1.7–6.2) 1.6 (1.4–3.9) 5.4 (2.6–10.9) < 0.001
Respiratory rate 22 (17–27) 24 (17.2–30) 22 (18–28) 24 (16–34) 0.183
PaO2/FiO2 207 (175–252) 193 (167–226) 128 (120–149) 133 (105–153) < 0.001
SpO2/FiO2 243 (231–265) 232 (200–245) 165 (154–170) 158 (136–176) < 0.001
Vasopressor use in first 24 h 100 (47.0) 102 (70.3) 6 (35.3) 67 (82.72) < 0.001
ARDS class after 24 h
 Mild ARDS 122 (57.3) 61 (42.1) 0 0 5 (6.2) < 0.001
 Moderate ARDS 91 (42.7) 84 (57.9) 15 (88.2) 59 (72.8) < 0.001
 Severe ARDS 0 0 0 0 2 (11.8) 17 (21) < 0.001
Cause of ARDS
 Pulmonary 156 (73.2) 99 (68.3) 12 (70.6) 58 (71.6) 0.509
 Non-pulmonary 67 (31.5) 78 (53.8) 5 (29.4) 40 (49.4) 0.426
  1. Categorical variables: number (percentage); continuous variables: median (25–75 percentile)
  2. CCI Charlson Comorbidity Index, LIPS Lung Injury Prediction Score, APACHE acute physiology and chronic health evaluation, PEEP positive end-expiratory pressure, FiO 2 fraction of inspired oxygen, PaCO 2 arterial carbon dioxide tension, PaO 2 arterial oxygen tension, SpO 2 pulse oximetry oxygen saturation, ARDS acute respiratory distress syndrome