Table 2.
Respiratory, hemodynamic and tonometric measurements
| Parameter | Baseline (n = 8) | PEEP 10 (n = 8) | PEEP 15 (n = 8) | PEEP 20 (n = 7) | Ideal PEEP (n = 7) | P |
|---|---|---|---|---|---|---|
| PEEP (cmH2O) | 9 (4–12) | 10 | 15 | 20 | 12 (8–15) | |
| Mean airway pressure (cmH2O) | 13.2 (8–18.7) | 14 (12–17) | 19 (17–22.2) | 24 (22–26.4) | 16.2 (11.5–22.2) | 0.0001a |
| OI (cmH2O per mmHg) | 5.3 (2.9–12.4) | 7 (3–14.5) | 6.7 (4.1–12.3) | 7 (5–12.3) | 6.6 (2.9–12.3) | 0.3 |
| PaO2/FiO2 (mmHg) | 235 (144–388) | 210 (117–402) | 285 (154–412) | 333 (196–440) | 243 (164–467) | 0.0009b |
| PaCO2 (mmHg) | 36 (31–54) | 41 (28–63) | 42 (31–66) | 45 (32–60) | 43 (28–52) | 0.08 |
| Cardiac index (l min-1 m-2) | 4.6 (2.5–6.3) | 4.5 (2.5–6.9) | 4.3 (2–6.8) | 4.7 (2.4–6.2) | 5.1 (2.1–6.3) | 0.08 |
| LVSWI (g m m-2) | 45 (22–71) | 43 (22–60) | 40 (14–60) | 36 (15–58) | 42 (14–66) | 0.13 |
| MAP (mmHg) | 79 (74–103) | 81 (69–99) | 74 (69–97) | 74 (66–93) | 73 (69–96) | 0.24 |
| PAOP (mmHg) | 16 (10–19) | 17 (8–22) | 17 (11–23) | 18 (12–26) | 14 (11–23) | 0.22 |
| CVP (mmHg) | 14 (9–17) | 15 (7–19) | 15 (9–24) | 15 (10–19) | 12 (8–18) | 0.27 |
| CO2 gap (mmHg) | 19 (2–30) | 19 (0–40) | 18 (0–39) | 17 (4–39) | 19 (9–39) | 0.18 |
Results are presented as median (range). CVP, central venous pressure; CO2 gap, arterial partial pressure of CO2 [pCO2] minus gastric pCO2; FiO2, fraction of inspired oxygen; LVSWI, left ventricular stroke work index; MAP, mean arterial pressure; OI, oxygenation index, defined as mean airway pressure × FiO2 × 100/arterial pCO2; PaO2, partial pressure of O2; PaCO2, partial pressure of CO2; PAOP, pulmonary arterial occlusion pressure; PEEP, positive end-expiratory pressure. aP < 0.05 for all comparisons except baseline versus PEEP 10 and PEEP 10 versus ideal PEEP. bP < 0.05 for all comparisons except baseline versus PEEP 10, baseline versus PEEP 15, baseline versus ideal PEEP, and PEEP 15 versus ideal PEEP.