Table 2.
Ventilator settings, respiratory mechanics, arterial blood gases, quantitative CT analysis, neuromonitoring data, and hemodynamics in our cohort at PEEP = 5 and 15 cmH2O.
| Parameter | PEEP = 5 | PEEP = 15 | p |
|---|---|---|---|
| (N = 16) | (N = 16) | ||
| Ventilator settings and arterial blood gases | |||
| Tidal volume, median [IQR], ml/kg PBW | 7.4 [6.9–7.9] | 7.4 [6.9–7.9] | 0.999 |
| Respiratory rate, median [IQR], 1/min | 21 [18–23] | 21 [18–22] | 0.257 |
| Plateau pressure, median [IQR], cmH20 | 21 [18–22] | 30 [28–34] | <0.001 |
| Respiratory system compliance, median [IQR], ml/cmH20 | 30 [30–38] | 34 [28–41] | 0.759 |
| Venous admixture, median [IQR], (%) | 25.7 [15.1–32.3] | 21.6 [15–31.2] | 0.717 |
| Ventilation ratio, median [IQR] | 1.7 [1.5–2] | 1.9 [1.7–2.2] | 0.109 |
| pH, median [IQR] | 7.41 [7.36–7.45] | 7.45 [7.39–7.48] | 0.343 |
| PaO2, median [IQR], mmHg | 96 [81–108] | 98 [85–148] | 0.039 |
| SaO2, median [IQR], mmHg | 98 [97–100] | 99 [97–99] | 0.724 |
| PaCO2, median [IQR], mmHg | 40 [37–45] | 44 [41–49] | 0.034 |
| SvO2, median [IQR], mmHg | 72 [63–78] | 75 [68–78] | 0.453 |
| PaO2/FiO2, median [IQR], mmHg | 195 [163–216] | 195 [171–296] | 0.049 |
| Quantitative computed tomography analysis | |||
| Total lung volume (ml) | 2,704 [2,360–3,574] | 3,334 [2,883–4,228] | 0.001 |
| Total lung weight (g) | 1,076 [915–1,368] | 1,010 [884–1,365] | 0.679 |
| Gas volume (ml) | 1,693 [1,204–2,292] | 2,429 [1,862–2,864] | <0.001 |
| Mean attenuation (HU) | −601 [-671 –−557] | −677 [-724 –−618] | 0.001 |
| Hyper-aerated tissue (g) | 10 [3–17] | 23 [14–32] | 0.002 |
| Hyper-aerated tissue (% of total lung weight) | 0.8 [0.3–1.5] | 2 [1.4–2.3] | 0.001 |
| Normally aerated tissue (g) | 449 [382–592] | 533 [402–655] | 0.002 |
| Normally aerated tissue (% of total lung weight) | 45 [31.4–54.2] | 48 [35–55] | 0.008 |
| Poorly aerated tissue (g) | 250 [193–307] | 199 [167–278] | 0.023 |
| Poorly aerated tissue (% of total lung weight) | 22.4 [16.6–26.1] | 19.7 [13.1–21.6] | 0.017 |
| Non-aerated tissue (g) | 434 [213–563] | 344 [189–567] | 0.121 |
| Non-aerated tissue (% of total lung weight) | 30.1 [25–44.6] | 31.2 [21.2–39] | 0.017 |
| Neuromonitoring | |||
| ICP, median [IQR], mmHg | 14 [11–17] | 23 [19–26] | <0.001 |
| CPP, median [IQR], mmHg | 78 [71–82] | 63 [58–75] | 0.001 |
| FVs, median [IQR], cm/s | 112 [106–121] | 97 [55–116] | 0.036 |
| FVd, median [IQR], cm/s | 43 [32–51] | 19 [15–27] | 0.001 |
| FVm, median [IQR], cm/s | 65 [59–74] | 46 [31–56] | 0.001 |
| ONSD, median [IQR], mm | 4.5 [4.1–5.1] | 5.8 [5.4–6.4] | 0.001 |
| ICPTCD, median [IQR], mmHg | 21 [18–25] | 33 [31–45] | 0.001 |
| Hemodynamics | |||
| Mean arterial pressure, median [IQR], mmHg | 91 [87–97] | 90 [84–94] | 0.086 |
Data are presented as median [IQR, interquartile range]. IQR, interquartile range; PaO2, arterial partial pressure of oxygen, SaO2, arterial oxygen saturation; PaCO2, arterial partial pressure of carbon dioxide; SvO2, venous saturation of oxygen; PaO2/FiO2 (inspired fraction of oxygen); HU: Hounsfield Units; ICP, intracranial pressure; FVs, FVd, FVm, systolic, diastolic, mean flow velocity; ONSD, optic nerve sheath diameter; ICPTCD, intracranial pressure measured with transcranial Doppler (TCD); CPP, cerebral perfusion pressure.