Table 1 Demographic and clinical characteristics of the study participants
|  | Spontaeous breathing controls (N = 29) | Ventilated controls (N = 20) | ARDS patients (N = 55) | p value |
|---|---|---|---|---|
Age (years) | 50 [40–57] | 52.0 [41.3–68.5] | 56 [41–77] | 0.090 |
Sex ratio (male/female) | 21/8 | 17/3 | 43/12 | 0.582 |
BMI (kg/m2) | 24.5 [21.7–26.6] | 24.0[19.7–25.7] | 25.5[23.0–27.7] | 0.056 |
SOFA on admission |  | 7 [4.3–9] | 11 [8–13] |  < 0.0001 |
PH |  | 7.42 [7.39–7.43] | 7.38 [7.27–7.44] | 0.035 |
PaCO2 (mmHg) |  | 39.2 [36.1–44.0] | 39.8 [31.3–44.7] | 0.710 |
PaO2 (mmHg) |  | 106.5 [76.1–141.3] | 78.8 [66.0–98.0] | 0.002 |
FiO2 (%) |  | 40 [31.3–40.0] | 80 [60–100] |  < 0.001 |
Lactate (mmol/L) |  | 1.6 [1.3–1.8] | 2.7 [1.8–4.2] | 0.007 |
Oxygen saturation |  | 99.2 [97.7–100] | 95 [91–98] |  < 0.0001 |
PaO2/FiO2 (mmHg) |  | 331.6 [196.0–358.9] | 106.7 [80.0–140.0] |  < 0.0001 |
PEEP (cmH2O) |  | 5 [5–6.5] | 5 [5, 6] | 0.319 |
Tidal volume (ml/kg IBW) |  | 3.53 [3.25–4.21] | 6.81 [6.21–7.29] |  < 0.0001 |
Mechanical ventilation [n (%)] | Â | 20 (100%) | 55 (100%) | Â |
Duration of MV (d) |  | 8.5 [3–25.75] | 6 [3–10] | 0.317 |
Mortality at day 28 [n (%)] | Â | 4 (20%) | 21 (38.2%) | Â |
Cause of death [n (%)] | Â | Â | Â | Â |
 Sepsis |  | 0 | 10 (47.6%) |  |
 Pulmonary dysfunction |  | 1 (25%) | 5 (23.8%) |  |
 Neurologic dysfunction |  | 3 (75%) | 2 (9.5%) |  |
 Cardiac dysfunction |  | 0 | 2 (9.5%) |  |
 Multiple organ failure |  | 0 | 2 (9.5%) |  |
ICU length of stay (d) |  | 10 [4–26] | 7 [4–13] | 0.223 |
Causes for ICU admission [n (%)] | Â | Â | Â | Â |
 Infectious pneumonia |  | 0 | 24 (43.6%) |  |
 Extra-pulmonary sepsis |  | 0 | 11 (20%) |  |
 Post-operation |  | 14 (70%) | 7 (12.7%) |  |
 Trauma |  | 1 (5%) | 6 (10.9%) |  |
 Others |  | 5 (25%) | 7 (12.7%) |  |