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Table 2 Variations between early and persistent ARDS

From: Effects of early versus delayed application of prone position on ventilation–perfusion mismatch in patients with acute respiratory distress syndrome: a prospective observational study

Study variables

Early ARDS, n = 33

P

Persistent ARDS, n = 24

P

Supine

Prone

Supine

Prone

Ventilator setting

FIO2

0.4 [0.4, 0.6]

0.4 [0.4, 0.5]

0.01

0.5 [0.4, 0.65]

0.5 [0.4, 0.55]

0.05

Respiratory rate, /min

20 [17, 22]

20 [18, 22]

0.76

27 [20, 30]

26 [20, 30]

0.35

Positive end-expiratory pressure, cmH2O

8 [8, 10]

8 [8, 10]

0.26

8 [6, 10]

8 [6, 10]

0.98

Tidal volume, mL/kg predicted body weight

7 [6, 8.1]

7 [6, 8.1]

0.59

6.1 [5.1, 7.0]

6.1 [5.1, 7.0]

0.96

Respiratory mechanics

Plateau pressure, cmH2O

20.5 [18.6, 21.7]

19.6 [18.8, 21.0]

0.84

19.3 [16.7, 23.6]

20.6 [17.8, 23.4]

0.26

Driving pressure, cmH2O

11.0 [10.3, 12.6]

11.9 [9.4, 13.5]

0.62

12.3 [9.6, 13.6]

12.2 [11.4, 13.4]

0.24

Respiratory system compliance, ml/cmH2O

36.0 [31.2, 41.8]

35.9 [29.3, 44.0]

0.30

30.8 [26.8, 38.7]

29. 8 [23.6, 37.0]

0.04

Arterial blood gases

pH

7.40 [7.38, 7.45]

7.41 [7.38, 7.45]

0.54

7.39 [7.37, 7.45]

7.39 [7.35, 7.42]

0.98

PaCO2, mmHg

40.1 [37.8, 42.1]

38.3 [35.6, 40.5]

0.02

42.6 [39.7, 44.6]

42.3 [38.2, 52.6]

0.94

PaO2, mmHg

72.4 [66.8, 78.4]

82.6 [73.1, 97.8]

< 0.001

84.7 [73.9, 101.8]

84.8 [77.3, 102.9]

0.55

PaO2/FIO2

157 [121, 191]

190 [164, 245]

< 0.001

168 [136, 232]

177 [155, 232]

0.10

Ventilatory ratio

1.42 [1.24, 1.87]

1.30 [1.21, 1.60]

0.01

1.84 [1.43, 2.11]

1.72 [1.5, 2.06]

0.48

Electrical impedance tomography

VT distribution dorsal, %

36.5 [29.5, 42.6]

60.4 [47.9, 73.8]

< 0.001

36.9 [29.6, 45.7]

57.2 [44.9, 66.0]

0.002

Perfusion distribution dorsal, %

47.9 [42.5, 52.2]

59.1 [54.0, 65.7]

0.001

45.3 [41.1, 50.5]

56.6 [49.5, 64.2]

0.001

COV index

44.8 [41.6, 46.8]

54.6 [49.7, 58.6]

 < 0.001

44.3 [40.9, 47.5]

54.6 [49.1, 57.1]

 < 0.001

RVD index

6 [4, 8]

4 [4, 5]

 < 0.001

6 [4, 7]

5 [4, 6.5]

0.38

Shunt, %

11.4 [7.1, 18.5]

12.7 [6.9, 17.8]

0.21

12.3 [7.4, 20.6]

19.4 [12.6, 24.6]

0.002

Shunt, dorsal, %

8.2 [4.8, 13.8]

3.8 [1.5, 9.6]

0.005

7.7 [3.9, 12.6]

10.7 [6.2, 16.4]

0.04

Shunt, ventral, %

2.0 [0.6, 5.5]

5.7 [2.9, 9.9]

0.02

3.6 [1.4, 8.0]

5.5 [2.9, 11.9]

0.02

Dead space, %

14.2 [7.7, 21.9]

9.1 [5.3, 13.4]

0.004

11.9 [9.4, 16.5]

11.3 [5.9, 15.6]

0.15

Dead space, dorsal, %

3.3 [0.9, 5.5]

3.1 [1.3, 5.2]

0.64

3.7 [1.3, 6.6]

2.9 [0.9, 6.4]

0.16

Dead space, ventral, %

10.0 [5.2, 17.6]

5.9 [2.0, 8.8]

0.001

8.5 [6.5, 10.1]

6.9 [4.9, 10.2]

0.36

Dead space/shunt ratio

1.1 [0.5, 2.9]

0.7 [0.4, 1.7]

0.48

1.2 [0.4, 2.1]

0.6 [0.3, 1.1]

0.009

Dead space/shunt ratio, dorsal

0.4 [0.1, 0.9]

0.7 [0.2, 2.2]

0.22

0.3 [0.1, 1.4]

0.2 [0.1, 0.8]

0.14

Dead space/shunt ratio, ventral

2.0 [0.8, 6.0]

0.3 [0.1, 0.8]

 < 0.001

2.0 [0.8, 4.2]

1.1 [0.5, 2.7]

0.07

Total unmatched units, %

28.7 [24.6, 35.4]

22.8 [20.0, 26.8]

 < 0.001

26.9 [20.1, 31.4]

31.2 [24.5, 36.4]

0.02

Unmatched units, dorsal, %

13.0 [9.2, 20.6]

9.0 [5.5, 13.2]

 < 0.001

12.8 [10.0, 16.3]

17.3 [11.2, 20.2]

0.095

Unmatched units, ventral, %

14.8 [11.3, 18.4]

13.4 [9.4, 14.9]

0.094

12.4 [9.2, 16.9]

14.8 [11.2, 20.2]

0.179

Hemodynamic variables

Heart rate (beats per minute)

80 [69, 90]

81 [72, 95]

0.50

85 [69, 93]

85 [75, 93]

0.54

MAP (mmHg)

82 [74, 88]

82 [75, 90]

0.28

83 [68, 87]

74 [69, 87]

0.80

  1. ARDS acute respiratory distress syndrome, COV center of ventilation, RVD regional ventilation delay index, SBP systolic blood pressure, MAP mean arterial pressure
  2. Values are represented as median (interquartile range)
  3. p indicates Wilcoxon signed-rank tests between paired supine position and prone position values
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