Table 1.
Patients characteristics at low and high positive end-expiratory pressure
| Low PEEP (5 cmH2O) | High PEEP (15 cmH2O) | p | |
|---|---|---|---|
| ICP and hemodynamic parameters | |||
| ICP (mmHg) | 4.0 (2.0–10.0) | 7.0 (5.8–11.0) | < 0.001 |
| MAP (mmHg) | 81.0 (75.6–92.1) | 76.2 (67.4–90.0) | 0.002 |
| CPP (mmHg) | 74.7 (69.6–86.8) | 68.7 (60.6–82.7) | < 0.001 |
| CVP (mmHg) | 8.0 (5.0–10.0) | 12.0 (10.0–14.0) | < 0.001 |
| Respiratory mechanics parameters | |||
| VT (mL/kg) | 7.7 (7.1–8.3) | 7.7 (7.1–8.2) | 0.304 |
| ∆PAW (cmH2O) | 6.8 (6.5–9.5) | 9.5 (7.8–10.9) | < 0.001 |
| ∆PCW (cmH2O) | 2.7 (1.4–3.1) | 2.7 (2.7–4.1) | 0.003 |
| ∆PL (cmH2O) | 4.8 (4.1–5.8) | 6.8 (4.1–8.2) | 0.003 |
| ERS (cmH2O/L) | 15.3 (12.5–18.6) | 20.1 (16.2–23.9) | < 0.001 |
| ECW (cmH2O/L) | 5.5 (2.9–6.9) | 6.2 (5.4–10.2) | 0.001 |
| EL (cmH2O/L) | 9.4 (7.9–12.1) | 12.9 (8.5–15.6) | 0.004 |
| ECW/ERS ratio | 0.33 (0.25–0.43) | 0.40 (0.29–0.47) | 0.247 |
| Resistance (cmH2O/L/sec) | 13.0 (9.9–14.2) | 12.6 (10.1–15.0) | 0.894 |
| Blood gas analysis parameters | |||
| pH | 7.40 (7.36–7.44) | 7.42 (7.38–7.45) | 0.951 |
| PaO2 (mmHg) | 105.5 (78.0–153.5) | 115.5 (78.4–163.5) | 0.058 |
| PaO2/FiO2 | 264 (180–384) | 289 (185–388) | 0.061 |
| PaCO2 (mmHg) | 35.3 (32.6–36.7) | 35.3 (33.6–38.2) | 0.052 |
| PETCO2 (mmHg) | 29.5 (27.8–31.2) | 29.0 (25.8–30.3) | 0.003 |
| VDalv/VT (%) | 13.2 (8.5–19.9) | 18.8 (11.9–27.7) | < 0.001 |
Data are shown as median (interquartile range)
ICP intracranial pressure; MAP mean arterial pressure; CPP cerebral perfusion pressure; CVP central venous pressure; VT tidal volume; ∆PAW airway driving pressure; ∆PCW chest wall driving pressure; ∆PL: transpulmonary driving pressure; ERS respiratory system elastance; ECW chest wall elastance; EL lung elastance; PETCO2 end-tidal carbon dioxide partial pressure; VDalv/VT: ratio of the alveolar dead space to the tidal volume