Table 1 Demographics, comorbidities, and clinical parameters of the study subjects

Male gender, n (%)

28 (66.7)

49 (69.0)

31 (77.5)

Age, mean ± SD (y)

66.7 ± 16.8

68.1 ± 16.2

65.3 ± 16.9

BMI, mean ± SD (kg/m²)

20.4 ± 4.0

20.5 ± 4.5

20.6 ± 4.2

Body temperature

37.4 ± 0.9

37.7 ± 1.4

37.5 ± 2.6

Underlying pneumonia (bacterial/aspiration/VAP^a)

8/17/4

28/19/1

20/7/0

 chronic heart disease

25%

24%

23%

 chronic respiratory disease

13%

18%

34%

 chronic kidney disease

19%

18%

25%

 glucose intolerance

24%

21%

25%

 connective tissue disease

2%

10%

15%

Direct lung injury

71%

87%

78%

Sepsis

81%

62%

58%

Use of catecholamine

36%

39%

58%

Immunosuppressant usage

22%

16%

18%

 APACHE II score

20.9 ± 6.5

23.6 ± 5.8

27.7 ± 8.4

 SOFA score

9.3 ± 3.1

10.7 ± 3.0

12.8 ± 3.9

 SAPS II score

55.4 ± 13.9

61.5 ± 13.5

65.9 ± 16.8

 White blood cell (× 10³/mm³)

16.1 ± 8.3

13.1 ± 8.1

13.4 ± 12.6

 Platelet (× 10³/mm³)

209 ± 135

196 ± 146

171 ± 152

 Total bililubin (mg/dL)

2.1 ± 4.4

1.6 ± 3.6

2.8 ± 7.0

 Creatinine (mg/dL)

1.4 ± 1.4

1.4 ± 1.3

1.9 ± 1.6

 C-reactive protein (mg/dL)

10.6 ± 9.0

12.2 ± 10.4

14.3 ± 12.1

 LDH (IU/L)

334 ± 181

339 ± 182

436 ± 259

 HCO₃⁻ (mEq/L)

24.9 ± 10.4

25.9 ± 6.7

25.5 ± 9.1

 PaCO₂ (Torr)

41.0 ± 9.6

47.4 ± 18.8

46.7 ± 15.7

 Lactate (mmol/L)

1.7 ± 1.2

2.5 ± 2.8

3.7 ± 4.2

HRCT score

151 ± 43

182 ± 71

204 ± 80

 Max. inspiratory pressure (cmH₂O)

17.0 ± 7.7

20.5 ± 6.8

21.4 ± 6.9

 Respiratory rate (breaths/min)

23 ± 6

27 ± 8

28 ± 10

 PEEP (cmH₂O)

8 ± 3

10 ± 4

11 ± 4

 FiO₂

0.43 ± 0.10

0.46 ± 0.10

0.5 ± 0.12

 Ventilator-free days

18.0 ± 8.1

11.5 ± 9.6

6.2 ± 8.8

 ICU free days

14.7 ± 8.2

11.9 ± 8.4

5.8 ± 7.5

 30-day mortality (%)

4 (10%)

16 (23%)

22 (55%)