prone position in ards - wsrc · prone positioning greatly reduces pro-inflammatory mediator...
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Prone Position in ARDS
Rich Kallet MS RRT FAARC, FCCMRespiratory Care Services
San Francisco General HospitalUniversity of California, San Francisco,
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Case Study• A 39 yo F admitted to SFGH TICU s/p hanging, cardiac
arrest, massive aspiration, severe hypoxemia, asynchrony and hemodynamic instability.
• Pre-prone management:– PEEP: +15, FiO2: 0.90– NMBA & Aeroprost 50 ng/kg/m
– VT: 530 mL (8.5); VE:17L/m– Pplat: 31 cmH2O; Crs: 33 mL/cmH2O
– ABG: 7.28 / 66/ 105 – P/F = 117 ; VD/VT = 0.92, a/APO2 = 0.16
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This presentation is sponsored by Hamilton Medical
I have no conflict of interest as it relates to this topic
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0.16
0.53
0.360.42
0.92
0.72 0.710.67
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SP P1 P2 P3
a/APO2 Vd/Vt
1h 2h 20h
P/F 117 351 232 265FiO2 0.90 0.90 0.60 0.50
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Percent Contribution of Ventral-Dorsal Lung Level to Total Area of the Lung by CT Analysis
18%
30%
52%
Gattinoni Anesthesiology 1991
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Pulmonary Stress-Strain: Supine vs. Prone Position
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Broccard et al. Crit Care Med 2000
Increased Dorsal:Caudal Ventilation with Prone Position
SUPINE
PRONE
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Prone Positioning as LPV
↓ Overinflation
↓ Nonaerated
↑ Well Aerated
Galiatsou 2006
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Supine Prone:
“Inflammatory cell activity present throughout the lungs independent of the inflation status.”
Gattinoni ,2013
Non-Dependent
Dependent
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Prone Positioning Greatly Reduces Pro-Inflammatory Mediator Release in ARDS
Chan (2007): RCT (N=22) ARDS-CAP, 72h PPMortality on ARDS Day 14 predicted by IL-6 (378 vs. 206 pg/mL)
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BL H-24 H-72
323274 278
396
293
196
Effect of Prone Position on IL-6 Expression
SP PP
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Complexity of Pulmonary Perfusion Distribution
• Whole Lung Level: Gravity: Hydrostatic Pressures– ↑lung tissue dorsal-caudal regions →↑vascularity →↑
perfusion/unit lung volume (upright position)
• Intermediate Level: Vascular tree geometry dominant
• 23 generations uneven branching angles/diameters that mimic airway structures (fractal geometry)
• Heterogenous perfusion within horizontal tissue plane as well as vertical zones
• Perfusion is largely independent of gravity : regardless of body posture, perfusion is always greater in dorsal lung regions (an“anatomical flow bias favoring dorsal perfusion” that is further enhanced by increased dorsal NO production)
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Impact of PP in ARDS(33 observational studies since 1976)
• N = 735
• Responders: 80% [57-100%]
• + Response both in Early & Late ARDS
• + Response both in ARDSpulm & ARDSextpulm
• ↑PaO2: 40 [26-52]; ↑PaO2/FiO2: 67 [8-161]
• Low incidence of adverse hemodynamic effects (2-4%)
• ↑ secretion mobilization some patients
• Mixed results: effects on PaCO2, Crs, EELV
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PROSEVA Study
N Engl J Med 2013
Multi-center RCT N = 466: 90 Day mortality ↓ 41 to 24% Adjusted RR for mortality 0.48 (SOFA); ↑ VFD 4 & 14 (D-28,D-90)↑ No difference in complication rates
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Meta-Analyses of RCT
• 11 RCTs comparing PP to SP• Pre-LPV, varying PP duration, varying ARDS
severity/etiology• PROSEVA study: 1st RCT + mortality benefit• Meta-analysis studies varied: reviewing 7, 9,
10 & 11 RCT’s
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Meta-Analyses of RCT• Sud (2010) : 10 studies; N = 1867,
– ↓Mortality P/F < 100 (RR: 0.84) effect up to P/F = 140– ↑ P/F: 27-39% over 3 days;– ↑ Pressure Ulcer (RR: 1.29)– ↑ ETT obstruction (RR: 1.58)
• Lee (2014) 11 studies; N = 2246– ↓Mortality (RR: 0.77); # to Tx: 16
– * PP > 10h (RR: 0.62)
– + Effect: P/F < 150 (RR: 0.72)– ↑ Pressure Ulcer (RR: 1.49)– ↑ ETT obstruction (RR: 1.55)
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Meta-Analyses of RCT
• Beiter (2014): 7 studies ; N = 2119– ↓Mortality (RR: 0.66) only when VT < 8 mL/kg
– ↓Baseline VT 1mL/kg PBW, ↓Mortality risk 16.7%
– PP > 12h/day ↓Mortality (RR: 0.71)
• Hu (2014): 9 studies; N = 2242 – ↓Mortality P/F < 100 (RR: 0.71);
– PEEP> 10 (RR: 0.57)
– PP > 12h/day (RR: 0.54)
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Prone Positioning,PEEP, RM: Manifestation of CREEP!
Progressive ↑ in pulmonary volume occurring under constant airway pressure (lungs & chest wall).
Viscoelastic property* of tissue that “yield” their shape over time under constant stress
“Slow” gradual ↑ in Oxygenation
*think of the properties of caramel or drying glue
Van de Woestijne 1967, Respir Physiol
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Recruitment = Pressure x Time
Dynamic process, variable time course.
Time Required: ↑ Viscosity = ↑ time necessary to open sequentially collapsed airways & alveoli
Paw needed to recruit collapsed small airways is determined by:
– Viscosity, thickness, surface tension of the airway lining fluid, – airway radius, – axial wall traction exerted by the surrounding alveoli, – presence of surfactant.
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Increased PP Time Enhances Oxygenation 25% Early (< 4h); Late? No plateau in P/F after 8h
Responders
Non-Responders
Reutershan Clin Sci 2006
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PP Enhances Effectiveness of PEEP in ARDSGrannier et al Intensive Care Med 2003
PP
Qs/Qt
PaO2 / Fi O2
PP
SP
PP
SP
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PP Enhances Inhaled Vasodilators in ARDS
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SP SP+NO PP PP+NO
165
191
219
263
164
138
175
134
PaO2/FiO2 PVR
Johannigman 2001
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Oczenski Crit Care Med 2005
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SP PP-6h PP-RM RM+30 RM+180
147
225
368351 364
Effect of Adding RM to Prone Positioning on PaO2/FiO2 in ARDS
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Prone Positioning Unloads the Right Ventricle & Decreases PFO-Related Shunt
• Cor-Pulmonale: 22% of ARDS cases– ARDS+Cor-Pulmonale 60% vs. 36% Mortality – PP in ARDS pts w/ Cor-Pulmonale– 33% ↓RV size/ 18h in PP; ↑CI 2.9 to 3.4– Associated w/ ↑oxygenation, ventilation, Crs
• PFO: ~20% of ARDS case related to Cor-Pulmonale– Case Report of severe PFO by TE-Echocardiography– PP immediate ↓ in bubble emboli transversing artia & – ↑ PaO2/FiO2 59 to 278 mmHg; ↓ PaCO2 54 to 30 mmHg
Viellard-Baron 2007 Cor Pulmonale; Legras 1999 PFO
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Lung recruitability with PP in ARDS has stronger association with ∆PaCO2 than ∆PaO2/FiO2
Protti, Intesive Care Med 2009
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Obesity and Prone Position
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P/F SP P/F PP
113
174
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222
BMI 25 BMI 38
De Jong 2013
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Screening Criteria for PP: Trial of PEEP: 14-18 cmH2O in Patients with PaO2/FiO2 < 150 on FiO2 > 0.60
Superimposed hydrostatic pressurein ARDS
Superimposed hydrostatic pressure+ CW Pressure in ARDS
Patients that have brisk oxygenation response to moderately high PEEP within a few hours don’t require PP
Cressoni 2014
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Frequency Distribution of Critical Opening Pressure in 200 Patients with ARDS
Set PEEP = LIP + 2-3 cmH2O
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Summary
• PP significantly ↑oxygenation 80% of ARDS• Early application w/ LPV & > 12h ↓ mortality• Enhances PEEP, RM, inhaled Vasodilators• Enhances LPV (max recruit, min overdistension)
• Enhances Secretion clearance in some patients• Skin erosion is a significant problem• Hemodynamic AE’s and catheter loss relatively
infrequent