Background
Methods
Study design and participants
Experimental protocol
Measurement of variables
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Absolute inspiratory transpulmonary pressure (PL,es) = Pplat − end-inspiratory esophageal pressure;
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Elastance-related transpulmonary pressure (PL,EL) = Pplat × (lung elastance/respiratory system elastance) [18];
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PLexpi = total PEEP − end-expiratory esophageal pressure;
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Airway driving pressure (DPaw) = Pplat − total PEEP;
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Transpulmonary driving pressure (DPL) = DPaw − (end-inspiratory − end-expiratory esophageal pressure);
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Elastance-related driving pressure = DPaw × (lung elastance/respiratory system elastance).
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Respiratory system elastance = (Pplat − total PEEP)/VT;
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Lung elastance = DPL/VT;
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Respiratory system elastance = Lung elastance + Chest wall elastance.
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Estimated recruitment volume (Vrec in ml) = (EELV at high PEEP − EELV at low PEEP) − ((VT/(Pplat − low PEEP) × (high PEEP − low PEEP)). [19]
Statistical analysis
Results
Characteristic | |
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Male, n (%) | 13 (68.4) |
Age (years) | 72 ± 10 |
Body mass index (kg/m2) | 28 ± 6 |
SAPS II score | 65 ± 15 |
Etiology of ARDS, n (%) | |
Pneumonia/aspiration | 16 (84.2) |
Sepsis | 2 (10.5) |
Pancreatitis | 1 (5.3) |
Organ failure at baseline (SOFA), n (%) | |
Hemodynamic | 18 (94.7) |
Renal | 9 (47.4) |
Hepatic | 0 (0) |
Hematological | 2 (10.5) |
Arterial blood gas | |
PaO2/FiO2 ratio | 92 ± 31 |
FiO2 (%) | 80 ± 21 |
pH | 7.31 ± 0.11 |
PaCO2 (mmHg) | 45 ± 10 |
HCO3- (mmol/l) | 22.4 ± 4.0 |
Base excess | − 3.4 ± 5.1 |
Lactates (mmol/l) | 1.6 ± 1.0 |
Hemodynamic variables | |
Heart rate (beats/min) | 99 ± 27 |
Systolic arterial pressure (mmHg) | 127 ± 23 |
Diastolic arterial pressure (mmHg) | 59 ± 12 |
Mean arterial pressure (mmHg) | 82 ± 13 |
Respiratory mechanics | |
Minute ventilation (L/min) | 9.6 ± 1.6 |
Tidal volume (ml/kg PBW) | 6.1 ± 0.4 |
EELV (ml) | 1319 ± 626 |
Aspect of ARDS, n (%) | |
Patchy | 6 (31.6) |
Diffuse | 10 (52.6) |
Focal | 3 (15.8) |
Mortality at Hospital discharge | 10/19 (53%) |
PEEP levels, oxygenation and alveolar recruitment
Protocols | PEEPbaseline | Express protocol |
P
Lexpi
| p value |
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PEEP (cmH2O) | 7.0 ± 1.8 | 14.2 ± 3.6* | 16.7 (5.9)* | < 0.0001 |
Pplat (cmH2O) | 20.8 ± 4.0 | 28.8 ± 2.0 * | 33.9 ± 10.6* | < 0.0001 |
PL,es (cmH2O) | 7.0 ± 5.9 | 11.9 ± 6.2* | 15.5 ± 8.5* | 0.0013 |
PL,EL (cmH2O) | 15.3 ± 4.9) | 20.5 ± 4.7* | 24.3 ± 11.4* | 0.0025 |
PLexpi (cmH2O) | − 2.6 ± 5.2 | 1.4 ± 5.1* | 3.3 ± 1.6* | < 0.0001 |
EELV (ml) | 1546 ± 634 | 2067 ± 924* | 2287 ± 945* | 0.001 |
DPaw (cmH2O) | 13.0 ± 3.9 | 14.2 ± 5.0 | 16.4 ± 7.8 | 0.17 |
DPL (cmH2O) | 9.9 ± 4.4 | 10.6 ± 5.6 | 12.3 ± 8.3 | 0.20 |
DPL,EL (cmH2O) | 7.5 ± 4.3 | 8.1 ± 5.6 | 9.5 ± 8.1 | 0.30 |
Crs (ml/cmH2O) | 33.3 ± 15.8 | 30.0 ± 10.7 | 28.3 ± 13.2 | 0.17 |
Ecw (cmH2O/l) | 8.7 ± 2.7 | 9.6 ± 3.4* | 10.9 ± 4.3* | 0.03 |
EL (cmH2O/l) | 26.0 ± 11.9 | 28.0 ± 15.9 | 33.2 ± 25.1 | 0.25 |
FiO2 (%) | 80.0 ± 21.1 | 80.6 ± 21.2 | 81.1 ± 21.6 | 0.46 |
PaO2/FiO2 | 91.2 ± 31.2 | 134.0 ± 67.2* | 152.7 ± 80.1* | 0.01 |
pH | 7.31 ± 0.11 | 7.30 ± 0.11 | 7.31 ± 0.12 | 0.08 |
PaCO2 (mmHg) | 45.2 ± 10.4 | 46.5 ± 9.6 | 45.3 ± 11.0 | 0.26 |
MAP (mmHg) | 82.0 ± 13.4 | 74.7 ± 12.9 | 75.7 ± 12.0 | 0.06 |
Heart rate (beats/min) | 99 ± 27 | 102 ± 26 | 107 ± 28 | 0.19 |
Lactates (mmol/l) | 1.6 ± 0.9 | 1.5 ± 0.8 | 1.5 ± 0.8 | 0.27 |