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Table 2 Respiratory mechanics, gas exchange, CT scan variables and outcome of the patients divided according to lower or higher airway driving pressure at PEEP 5 cmH2O

From: Airway driving pressure and lung stress in ARDS patients

Variable

Overall population (N = 150)

Lower airway driving pressure (<15 cmH2O) (N = 108)

Higher airway driving pressure (≥15 cmH2O) (N = 42)

p value

Airway driving pressure (cmH2O)

12.6 [10.3–15.2]

11.6 [10.0–13.1]

16.9 [15.7–18.9]

<0.001

Transpulmonary driving pressure (cmH2O)

9.0 [7.3–11.7]

8.1 [6.5–9.8]

13.6 [11.7–15.1]

<0.001a

End-inspiratory airway plateau pressure (cmH2O)

18.2 [16.2–20.9]

17.2 [15.6–18.7]

22.5 [20.9–24.0]

<0.001

Lung stress (cmH2O)

13.5 [10.7–16.0]

11.8 [10.0–14.0]

17.5 [15.4–18.9]

<0.001a

Respiratory system elastance (cmH2O/L)

25.2 [19.8–30.5]

22.1 [18.7–26.7]

33.6 [29.6–40.4]

<0.001

Lung elastance (cmH2O/L)

17.5 [13.9–23.2]

15.4 [12.7–19.9]

27.4 [21.9–31.6]

<0.001

Chest wall elastance (cmH2O/L)

6.3 [4.3–9.0]

5.9 [4.3–8.7]

7.8 [4.6–10.4]

0.054

PaCO2 (mmHg)b

44.2 [39.9–50.5]

43.9 [39.2–50.5]

47.6 [41.3–50.7]

0.117a

PaO2/FiO2 ratiob

143 [98–177]

145 [104–178]

132 [81–176]

0.404

Lung total gas (mL)c

1058 [721–1662]

1234 [879–1827]

694 [562–903]

<0.001

Total lung tissue weight (g)b

1394 [1145–1684]

1369 [1173–1742]

1457 [1050–1682]

0.787

• Non-aerated lung tissue (%)b

45.2 [34.0–56.9]

44.9 [36.6–53.6]

50.4 [30.7–61.1]

0.419a

• Poorly aerated lung tissue (%)b

28.1 [20.2–39.2]

27.1 [20.1–36.1]

34.1 [20.3–43.0]

0.067

• Well-aerated lung tissue (%)b

23.9 [14.2–33.9]

28.2 [17.2–34.6]

16.5 [8.2–26.7]

0.006

• Over-aerated lung tissue (%)b

0.01 [0.00–0.17]

0.03 [0.00–0.29]

0.00 [0.00–0.02]

0.002

Lung recruitability (%)b

15.6 [7.9–23.7]

12.5 [7.5–22.1]

18.5 [9.7–26.4]

0.110

ICU mortality N (%)

48 (32.0)

29 (26.9)

19 (45.2)

0.049

  1. Lung mechanics, gas exchange, CT-related variables and lung total gas were determined at PEEP 5 cmH2O. Statistical analysis: Student’s t testa, Mann-Whitney rank sum test, chi-square, as appropriate
  2. Abbreviations: CT computed tomography, PEEP positive end-expiratory pressure, PaCO 2 arterial partial pressure of carbon dioxide, PaO 2 arterial partial pressure of oxygen, FiO 2 inspired fraction of oxygen, ICU intensive care unit
  3. bData available for 91 patients (59 in the “lower airway driving pressure” group and 32 in the “higher airway driving pressure” group)
  4. cTotal gas was computed either by CT scan analysis (in 59 and 32 patients, respectively), or by helium dilution technique (in 48 and ten patients, respectively)