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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)