Table 1 Changes in hemodynamics, gas exchange, respiratory mechanics, and pulmonary regional ventilation between high and low PEEP in supine (n = 10)
High PEEP | Low PEEP | P | |
|---|---|---|---|
Clinical variables | |||
Heart rate, beats.min−1 | 72 [64–95] | 76 [59–97] | 0.977 |
Systolic arterial blood pressure, mmHg | 125 [108–138] | 129 [118–140] | 0.555 |
Diastolic arterial blood pressure, mmHg | 63 [49–69] | 58 [48–65] | 0.158 |
Mean arterial blood pressure, mmHg | 77 [72–89] | 77 [73–86] | > 0.999 |
Transpulmonary thermodilution indices | |||
Cardiac index, L.min−1.m−2 | 2.5 [2.0–3.0] | 2.6 [2.2–3.3] | 0.027 |
Global end-diastolic volume indexed, mL.m−2 | 661 [551–870] | 668 [559–813] | 0.432 |
Extravascular lung water, mL.kg−1 | 15 [13–18] | 14 [13–17] | 0.551 |
Pulmonary vascular permeability index | 3.3 [2.7–3.9] | 3.3 [2.7–3.6] | 0.607 |
Cardiac function index, min−1 | 4.4 [2.4–5.3] | 4.5 [2.8–5.8] | 0.008 |
Gas exchanges | |||
pH | 7.35 [7.29–7.37] | 7.35 [7.30–7.41] | 0.305 |
PaCO2, mmHg | 45 [39–51] | 44 [40–47] | 0.191 |
PaO2/FiO2 ratio, mmHg | 116 [99–196] | 106 [86–129] | 0.127 |
SaO2, % | 97 [95–98] | 96 [92–97] | 0.172 |
VD/VT | 0.34 [0.29–0.39] | 0.35 [0.30–0.39] | 0.348 |
A-a gradient, mmHg | 374 [304–533] | 384 [275–543] | 0.139 |
Respiratory mechanics | |||
Respiratory rate, breaths.min−1 | 27 [23–30] | 27 [23–30] | – |
Tidal volume, mL.kg−1 IBW | 6.0 [6.0–6.3] | 6.0 [6.0–6.3] | – |
Positive end-expiratory pressure, cmH2O | 16 [16–16] | 8 [8–8] | 0.016 |
Peak pressure, cmH2O | 44 [42–47] | 35 [33–36] | 0.002 |
Plateau pressure, cmH2O | 28 [27–31] | 20 [18–21] | 0.002 |
Driving pressure, cmH2O | 14 [11–16] | 12 [10–13] | 0.004 |
End-expiratory transpulmonary pressure, cmH2O | 6 [4–8] | 2 [− 1–4] | 0.002 |
End-inspiratory transpulmonary pressure, cmH2O | 14 [13–17] | 9 [6–10] | 0.002 |
Respiratory system compliance, ml.cmH2O−1 | 29 [27–36] | 34 [30–42] | 0.012 |
Respiratory system resistance, cmH2O.L−1.sec−1 | 0.24 [0.20–0.25] | 0.23 [0.22–0.26] | > 0.999 |
Lung compliance, ml.cmH2O−1 | 47 [40–56] | 64 [46–82] | 0.008 |
R/I ratio | 0.33 [0.21–0.54] | – | |
End-expiratory lung volume, mL | 2546 [2151–3019] | 1725 [1450–2023] | 0.002 |
Electrical impedance tomography derived indices | |||
Dorsal fraction, % | 46 [43–54] | 35 [32–39] | 0.002 |
Global inhomogeneity index, % | 58 [52–60] | 60 [55–66] | 0.059 |
End-expiratory lung impedance | 251 [179–404] | 139 [83–243] | 0.008 |
Changes in end-expiratory lung impedance, % | −118 [− 150 to − 32] | 0.004 | |