Table 1 Electrical impedance tomography data analysis of selected physiologic variables, respiratory parameters, and hemodynamic parameters at the four different time points

EIT data

Ventilation distribution, ventral (%)

68.87 ± 10.94

61.04 ± 12.80^a

58.66 ± 12.51^a

55.83 ± 13.48^a

 < 0.001

Ventilation distribution, dorsal (%)

31.13 ± 10.94

38.96 ± 12.80^a

41.34 ± 12.51^a

44.17 ± 13.48^a

 < 0.001

Ventilation distribution, ROI 1 (%)

16.01 (9.93–22.39)

10.99 (7.40–16.66)^a

12.95 (9.13–15.35)

12.05 (7.30–15.68)^a

0.009

Ventilation distribution, ROI 2 (%)

52.12 ± 5.54

48.81 ± 9.34

46.07 ± 8.73

42.88 ± 9.24^a

0.002

Ventilation distribution, ROI 3 (%)

26.62 ± 10.21

33.42 ± 9.37

36.56 ± 10.75^a

35.51 ± 11.11^a

0.001

Ventilation distribution, ROI 4 (%)

4.52 ± 3.58

5.56 ± 6.40

4.78 ± 5.57

8.66 ± 5.32^a

0.027

Perfusion distribution, ventral (%)

57.75 (53.81–67.97)

56.20 (52.72–61.52)

57.37 (47.63–63.24)

49.62 (46.80–58.74)^a

0.013

Perfusion distribution, dorsal (%)

42.25 (32.03–46.19)

43.80 (38.48–47.28)

42.63 (36.76–52.37)

50.38 (41.26–53.20)^a

0.013

Perfusion distribution, ROI 1 (%)

15.86 ± 8.62

12.61 ± 4.54

12.54 ± 5.10

13.11 ± 4.91

0.405

Perfusion distribution, ROI 2 (%)

46.76 ± 9.18

44.43 ± 4.83

42.87 ± 5.64

38.99 ± 6.00^a

0.009

Perfusion distribution, ROI 3 (%)

36.32 (27.99–39.37)

37.82 (29.37–42.87)

36 (30.81–42.19)

39.47 (33.76–43.95)^a

0.037

Perfusion distribution, ROI 4 (%)

5.93 ± 3.16

6.45 ± 3.04

7.40 ± 3.71

9.00 ± 3.29^{a b}

0.005

GI index-ventilation

0.61 (0.55–0.62)

0.54 (0.51–0.61)

0.53 (0.47–0.55)^a

0.50 (0.42–0.53)^a

< 0.001

Center of Ventilation (%)

43.31 ± 5.07

45.09 ± 4.88

46.05 ± 4.63

46.84 ± 4.96^a

0.048

Shunt (%)

13.80 ± 7.53

10.15 ± 3.34

12.39 ± 8.37

8.39 ± 5.18

0.059

Shunt, ventral (%)

4.29 (1.94–7.03)

2.87 (1.07–5.66)

3.39 (1.79–6.62)

2.30 (1.02–3.57)

0.348

Shunt, dorsal (%)

7.38 (4.99–13.01)

6.41 (4.94–8.75)

5.60 (3.00–10.49)

4.80 (2.80–8.38)

0.458

Dead space (%)

23.92 (14.71–31.43)

25.54 (15.37–29.57)

18.19 (15.02–28.31)

26.81 (19.34–31.08)

0.777

Dead space, ventral (%)

8.30 ± 2.40

8.49 ± 2.45

9.25 ± 2.67

7.13 ± 2.06

0.906

Dead space, dorsal (%)

6.99 (4.70–9.13)

7.95 (4.60–10.64)

7.26 (4.40–9.86)

8.67 (6.27–13.02)

0.552

V/Q matching (%)

63.41 ± 13.47

69.13 ± 10.18

67.76 ± 13.25

68.58 ± 11.70

0.258

V/Q matching, ventral (%)

35.89 (30.51–43.33)

38.28 (34.23–42.30)

34.07 (27.65–43.14)

34.43 (31.38–36.78)

0.682

V/Q matching, dorsal (%)

25.72 ± 9.01

31.13 ± 6.62

33.14 ± 8.95^a

29.80 ± 7.19

0.007

Respiratory parameters

PaO₂

75.16 ± 17.19

–

–

116.1 ± 41.24

0.004

PaCO₂

44.27 ± 8.58

–

–

36.78 ± 4.20

0.032

PaO₂/FiO₂

109.5 ± 36.44

–

–

222.2 ± 58.46

< 0.001

Mean airway pressure (cmH₂O)

20.83 ± 2.21

20.75 ± 2.30

20.83 ± 2.13

20.50 ± 1.78

0.448

Total minute ventilation (L/min)

5.88 ± 0.90

6.14 ± 0.99

6.55 ± 1.19^a

7.53 ± 1.22^abc

 < 0.001

Tidal volume (mL/kg PBW)

6.90 ± 0.68

7.19 ± 0.74

7.66 ± 0.74^a

8.82 ± 0.84^abc

 < 0.001

Tidal volume (mL)

442.5 ± 32.86

461.3 ± 36.15

491.8 ± 38.8^a

567.5 ± 60.93^abc

 < 0.001

*Driving pressure (cmH₂O)

11.93 ± 1.73

11.40 ± 1.61

10.86 ± 2.15

10.30 ± 1.97

0.090

*Crs (mL/cmH₂O)

32.15 (27.11–42.3)

32.40 (29.63–39.98)

38.45 (30.15–45.53)

37.95 (36.00–44.25)

0.030

Hemodynamic parameters

Systolic blood pressure (mmHg)

118.3 ± 17.83

125.1 ± 16.18

125.4 ± 28.22

130.8 ± 26.98

0.624

Diastolic blood pressure (mmHg)

62 ± 9.42

64.75 ± 8.76

61.33 ± 13.9

65.67 ± 11.62

0.734

Heart rate (bpm)

103 ± 19.24

93.92 ± 17.71

90.67 ± 90.67

89.17 ± 12.48

0.185

Norepinephrine dose (μg/kg/min)

0 (0–0.246)

0 (0–0.17)

0.05 (0–0.15)

0 (0–0.15)

0.968