Introduction
Materials and methods
Study population
Patient | Sex (M/F) | Age (years) | Measured weight (kg) | BMI (kg/m2) | PEEP (cmH2O) | PaO2/FiO2 (Torr) | Diagnosis | Days of ALI/ARDS | Outcome |
---|---|---|---|---|---|---|---|---|---|
1 | M | 73 | 75 | 23,2 | 9.4 | 180 | Sepsis (from peritonitis) | 2 | S |
2 | F | 55 | 55 | 19,9 | 10.9 | 245 | Sepsis (from peritonitis) | 9 | S |
3 | M | 76 | 85 | 23,3 | 8.3 | 138 | Community-acquired pneumonia | 4 | S |
4 | M | 43 | 90 | 23,3 | 10.6 | 225 | Pneumonia (ab ingestis) – sepsis | 2 | S |
5 | M | 80 | 70 | 23,0 | 11.3 | 210 | Nosocomial pneumonia | 13 | S |
6 | M | 48 | 85 | 24,2 | 12.8 | 265 | Polytrauma | 8 | S |
7 | M | 44 | 80 | 24,7 | 9.3 | 178 | Nosocomial pneumonia | 6 | S |
8 | M | 38 | 92 | 23,3 | 8.8 | 225 | Pneumonia (ab ingestis) | 7 | S |
9 | M | 77 | 55 | 22,1 | 14.0 | 204 | Idiopathic pneumonia in bone marrow transplantation | 1 | D |
10 | M | 27 | 80 | 23,3 | 12.7 | 237 | Nosocomial pneumonia | 4 | S |
11 | M | 59 | 93 | 23,3 | 10.3 | 160 | Sepsis | 2 | S |
Overall | 10 M, 1 F | 56.4 ± 18.0 | 78.2 ± 13.4 | 23.1 ± 1.2 | 10.8 ± 1.81 | 206.2 ± 38.7 | – | 5.2 ± 3.7 | 1D, 10S |
Study design
Position | Units | Supine | Prone without supports | Prone with supports |
---|---|---|---|---|
Thorax | cmH2O | 15.4 ± 4.1 | 17.0 ± 7.4 | 29.0 ± 6.5a,b |
Abdomen | cmH2O | 5.8 ± 2.9 | 11.0 ± 1.8a | 0.0 ± 0.0a,b |
Sacrum/pubis | cmH2O | 8.0 ± 5.7 | 4.5 ± 4.2 | 28.3 ± 8.9a,b |
Global | cmH2O | 9.7 ± 5.8 | 10.8 ± 7.0 | 19.1 ± 15.2a,b |
Measurements
Contact pressures
Gas exchanges and hemodynamics
End-expiratory lung volume and respiratory mechanics
Statistical analysis
Results
Contact pressures
End-expiratory lung volume and respiratory mechanics
Variable | Units | Supine | Prone without support | Prone with support |
---|---|---|---|---|
Tidal volume (VT) | ml | 565.3 ± 160.5 | 577.6 ± 185.3 | 593.4 ± 200.7 |
Tidal volume per kg IBW (VT/kgIBW) | ml/kg | 7.2 ± 1.4 | 7.4 ± 1.6 | 7.6 ± 1.8 |
EELV | l | 1.12 ± 0.49 | 1.00 ± 0.26 | 1.07 ± 0.31 |
Mean airway pressure | cmH2O | 15.1 ± 2.1 | 15.6 ± 2.3 | 15.7 ± 2.1a |
Plateau pressure (Pplat) | cmH2O | 22.4 ± 4.3 | 22.1 ± 3.8 | 23.6 ± 4.5a,b |
Respiratory system compliance | ml/cmH2O | 52.1 ± 17.6 | 52.9 ± 18.8 | 49.3 ± 18.1b |
Lung compliance | ml/cmH2O | 71.5 ± 23.8 | 93.5 ± 47.3a | 102.0 ± 47.0a |
Chest wall compliance | ml/cmH2O | 235.2 ± 152.5 | 158.1 ± 77.8 | 102.5 ± 38.0a,b |
Transpulmonary pressure changec | cmH2O | 8.4 ± 2.2 | 7.1 ± 2.2a | 6.6 ± 2.3a |
Pleural pressure changec | cmH2O | 3.2 ± 1.9 | 4.3 ± 1.9 | 6.1 ± 1.8a,b |
Gastric pressure | cmH2O | 13.4 ± 4.0 | 14.3 ± 3.5 | 13.2 ± 4.3 |
Gastric pressure changec | cmH2O | 2.6 ± 0.8 | 3.4 ± 1.1a | 4.5 ± 1.9a,b |
Transdiaphragmatic pressure | cmH2O | 0.6 ± 2.0 | 0.9 ± 1.6 | 1.6 ± 1.7 |
Bladder pressure | cmH2O | 12.0 ± 2.8 | 14.5 ± 3.4a | 14.5 ± 3.7a |
Gas exchange
Variable | Units | Supine | Prone without supports | Prone with supports |
---|---|---|---|---|
PaO2/FiO2 | Torr [kPa] | 206.2 ± 38.7 [27.5 ± 5.2] | 261.8 ± 41.2a [34.9 ± 5.5] | 265.0 ± 40.0a [35.3 ± 5.3] |
PaO2 | Torr [kPa] | 87.7 ± 10.2 [11.7 ± 1.4] | 112.5 ± 16.0a [15.0 ± 2.1] | 113.4 ± 12.0a [15.1 ± 1.6] |
SaO2 | % | 95.7 ± 1.0 | 96.6 ± 0.6a | 96.7 ± 0.6a |
PvO2 | Torr [kPa] | 44.6 ± 4.0 [5.9 ± 0.5] | 49.0 ± 6.3a [6.5 ± 0.8] | 47.7 ± 5.6a [6.4 ± 0.7] |
SvO2 | % | 77.2 ± 4.4 | 80.3 ± 5.4a | 79.6 ± 5.7a |
pHa | 7.37 ± 0.06 | 7.37 ± 0.05 | 7.36 ± 0.06 | |
Ve | l/minute | 9.4 ± 2.5 | 9.6 ± 2.8 | 9.9 ± 3.1 |
PaCO2 | Torr [kPa] | 43.9 ± 4.2 [5.9 ± 0.6] | 43.6 ± 4.2 [5.8 ± 0.6] | 44.3 ± 6.1 [5.9 ± 0.8] |
PvCO2 | Torr [kPa] | 51.0 ± 6.6 [6.8 ± 0.9] | 52.1 ± 6.8 [6.9 ± 0.9] | 52.2 ± 6.4 [7.0 ± 0.9] |
pHv | 7.35 ± 0.05 | 7.34 ± 0.06 | 7.34 ± 0.05 | |
VCO2 | ml/minute | 145.5 ± 38.8 | 143.3 ± 40.9 | 140.4 ± 42.9 |
Vd/Vt | 0.62 ± 0.10 | 0.63 ± 0.11 | 0.63 ± 0.13 | |
Vd/Vt(alv) | 0.18 ± 0.15 | 0.19 ± 0.15 | 0.18 ± 0.16 |
Variable | Units | Supine | Prone without supports | Prone with supports |
---|---|---|---|---|
CI | (l/minute)/m2BSA | 3.2 ± 0.7 | 3.2 ± 0.6 | 3.1 ± 0.5 |
SVI | ml/m2BSA | 38.1 ± 7.2 | 37.8 ± 6.8 | 34.9 ± 5.4a,b |
HR | min-1 | 79.6 ± 17.3 | 82.1 ± 17.9 | 86.7 ± 16.7a,b |
Mean BP | mmHg | 83.7 ± 8.0 | 89.2 ± 9.4 | 85.2 ± 11.8 |
Systolic BP | mmHg | 123.0 ± 16.5 | 132.0 ± 18.4a | 123.8 ± 19.8 |
Diastolic BP | mmHg | 64.0 ± 7.6 | 67.8 ± 9.8 | 65.9 ± 9.8 |
Mean PAPc | mmHg | 27.4 ± 3.0 | 31.0 ± 6.6 | 27.1 ± 9.0b |
Systolic PAPc | mmHg | 38.6 ± 5.1 | 41.8 ± 11.3 | 36.8 ± 11.9b |
Diastolic PAPc | mmHg | 21.8 ± 1.9 | 25.6 ± 4.7 | 22.2 ± 7.5b |
WPd | mmHg | 22.0 ± 5.7 | 24.4 ± 6.6 | 23.2 ± 7.5 |
CVP | mmHg | 12.0 ± 2.3 | 13.0 ± 2.8 | 12.7 ± 4.3 |
Diuresis | ml | 111 ± 71 | 90 ± 64a | 91 ± 58a |
Hemodynamics
Discussion
Mechanics of the respiratory system
Lung volumes, gas exchange and hemodynamics
Clinical implications
Conclusion
Key messages
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The prone position is a recognized rescue therapy for severe hypoxemia in ARDS.
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Allowing free abdominal movement should improve lung mechanics and gas exchange on a theoretical basis.
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This hypothesis was tested by studying respiratory mechanics (partitioned into lung and chest wall components), gas exchange and hemodynamics with and without thoraco-pelvic supports.
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We could not show any benefit from using thoraco-pelvic supports.
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Thoraco-pelvic supports are useless in ARDS patients in the prone position and merely increase the likelihood of pressure sores, as a result of increased contact pressures.