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Ira M Cheifetz MDDuke Children's Hospital
Durham, NC
Dean R Hess PhD RRTMassachusetts General Hospital
Harvard Medical School
Boston, MA
PEEP: Bringing theEvidence to the Bedside
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16 yo with Crohns Disease
Immunosuppressed(mercaptopurine)
CMV pneumonia and diffuse
alveolar hemorrhage by BAL Febrile and pancytopenic (WBC
2K; HCT 26%; Plt 89K)
Intubated for severe hypoxemiawith tachypnea and dyspnea
Ventilator: VCV, VT 250 mL(6 mL/kg PBW), I:E 1:2, rate 26,
PEEP 14 cm H2O, FiO2 0.60
ABG: pH 7.41, PaCO2 41 torr,PaO2 64 torr
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The goal of PEEP in this patient is to:
A. Increase PaO2
B. Decrease FiO2
C. Decrease risk of VILI
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Preventing Overdistention and
Collapse Injury
Lung Protective Ventilation
V
OL
U
M
E
V
OL
U
M
E
PressurePressure
Limit Distending Pressure
Add PEEP
Limit Vt
Add PEEPAdd PEEP
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Few topics generate more controversy!
What is the role of PEEP in the reduction /prevention of VILI?
What is the role of PEEP with lung protective
ventilatory strategies?
What is optimal PEEP? Does it really exist?
How do you select the best PEEP for yourpatient?
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Edema in Rat Lungs after Ventilation
14/0 45/10 45/0
Webb HH et al. Am Rev Respir Dis. 1974;110:556-565.
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Does PEEP recruit alveoli?
Or, just prevent de-recruitment
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Inspiratio
n
Exhalation
Zone of
Atelectasis
Zone ofOverdistention
IdealPEEP
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53 patients: conventional vs. protective ventilation Conventional: lowest PEEP for acceptable
oxygenation and VT 12 mL/kg
Protective: PEEP above the lower inflection pointon the PV curve, VT < 6 mL/kg, recruitment
maneuvers, PCV
28 day mortality: protective-ventilation 38% vs.conventional-ventilation 71% (p< 0.001).
N Engl J Med 1998;338:347
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Control (n = 50): VT 911 mL/kg PBW,PEEP > 5 cm H2O
Pflex / LTV (n = 53): VT 58 mL/kg PBW,PEEP at Pflex +2 cm H2O
ICU mortality: 32% in Pflex/LTV group vs. 53% in
control group (p= 0.04)
Crit Care Med 2006; 34:1311
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A. Lower tidal volume only
B. Higher PEEP only
C. Combined effect of PEEP and tidal
volumeD. Unknown
Was the mortality difference in theAmato and Villar trials due to lowertidal volume, higher PEEP, or both?
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N Engl J Med 2000; 342:1301
861 ALI/ARDS patients (10 centers)
6 vs. 12 mL/kg PBW (VCV, Pplat 30 cm H2O)
25%in mortality with smaller tidal volume
Number-needed-to-treat: 12 patients
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ALVEOLI (Assessment of Low tidal Volume and
elevated End-expiratory volume to Obviate Lung Injury)
2 PEEP levels; VT 6 mL/kg PBW
Oxygenation and respiratory system compliancewere improved withPEEP
Stopped at 549 patients for futility
No safety concerns
N Engl J Med 2004;351:327
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Target VT 6 mL/kg PBW Control (n=508): Pplat 30 cm H2O (VCV), lower PEEP
Intervention (n=475): Pplat 40 cm H2O (PCV),
recruitment maneuvers (40 s at 40 cm H2O),initial PEEP 20 cm H2O
No significant difference in hospital mortality
Meade, JAMA 2008;299:637
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Target VT 6 mL/kg PBW Control (n=382): low PEEP (5-9 cm H2O)
minimal distension strategy
Experimental (n=385): PEEP set to achieve Pplat28-30 cm H2O (recruitment strategy);PEEP 163 cm H2O on day 1
No significant difference in mortality, butimproved lung function; reduced duration ofmechanical ventilation and organ failure
Mercat, JAMA 2008;299:646
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Why did these studies fail to show a
mortality benefit?
A. They were underpowered
B. Higher PEEP does not help
C. PEEP strategies were incorrect
D. Harm from higher Pplat offsets benefit ofPEEP
E. Unknown
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Benefit of Higher PEEP Offset by Higher Pplat?
LowerPEEP
HigherPEEP
6mL/kg
P
PlatorPEEP
(cmH2
0)
6 mL/kgNon-
recruitable 6 mL/kgRecruitable
Injury>
Benefit
Benefit>
Injury
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68 ALI/ARDS patients; chest CT at airwaypressures of 5, 15, and 45 cm H2O
Potentially recruitable lung varied
On average, 24% lung could not be recruited
Patients with a higher percent of potentially
recruitable lung had
oxygenation andrespiratory-system compliance, anddead space
N Engl J Med 2006;354:1775
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N Engl J Med 2006;354:1775
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FiO2 0.3 0.3 0.3 0.3 0.3 0.4 0.4 0.5 0.5 0.5 0.6 0.7 0.8 0.9 1.0
PEEP 5 8 10 12 14 14 16 16 18 20 20 20 20 20 20-24
FiO2 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0
PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 20-24
Assess lung recruitabilityPaO2/FiO2 < 150 on 5 cm H2O PEEP
compliance ordeadspace withPEEP?
no
yes
Ramnath, Clin Chest Med 2006;27:601
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Optimal PEEP by Compliance
15 normovolemic ventilated patients
with acute lung injury O2 transport anddeadspace
correlated with compliance
Optimal PEEP varied; 0-15 cm H2O PMVO2 increased from PEEP 0 to the
PEEP resulting in maximum O2transport, but thenat higher PEEP
Compliance may be used to indicatethe PEEP likely to result in optimumcardiopulmonary function.
PEEP
Suter, N Engl J Med 1975;292:284
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0 10 20 30 400
0.4
0.8
1.2
1.6
normal
ARDS
airway pressure (cm H2O)
volumeabove
FRC(liters)
lower inflectionpoint
upper inflectionpoint
0 10 20 30 400
0.4
0.8
1.2
1.6
normal
ARDS
airway pressure (cm H2O)
volumeabove
FRC(liters)
lower inflectionpoint
upper inflectionpoint
Pressure-Volume Curve
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Rotta, J Pediatr (Rio J) 2003;79(Suppl 2):S149
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Owens, Stigler, Hess; Clin Chest Med 2008; 29:297
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Issues with Static PV Curves
Requires sedation / paralysis
Difficult to identify inflection points(Harris, AJRCCM, 2000) May require esophageal pressure to separate lung
from chest wall effects (Mergoni, AJRCCM, 1997;Ranieri, AJRCCM, 1997)
Deflation limb may be more useful than inflation limb(Holzapfel, Crit Care Med, 1983; Hickling, AJRCCM, 2001)
Pressure-volume curves of individual lung units notknown (Hickling, AJRCCM, 1998)
Role of static PV curve for setting PEEP
currently unknown!
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Decremental PEEP Trail
Theoretically attractive, but unproven!
Hickling, AJRCCM 2001;163:69 Richard, Critical Care2004, 8:163
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Esophageal Balloon Catheter
Benditt, Respir Care 2005; 50:68
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Setting PEEP for Acute Lung Injury
0 cm H2O: likely harmful
8-15 cm H2O: appropriate in most patients
> 20 cm H2O: seldom necessary
PEEP should be selected in the context ofprevention of ventilator induced lung injury.
The benefit of precise setting of PEEP isunproven.
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Cardiorespiratory Economics
O2 Supply = O2 Delivery = DO2
DO2 = cardiac output x oxygen content
O2 content = (1.34 x Hgb x O2 sat) + (0.003 x PaO2)
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Determinants of Oxygen Delivery
Hgb (O2 capacity)O2 binding (SaO2)
O2 dissolved (PaO2)Oxygen Content
Contractility
Afterload
Preload
Stroke Volume
Heart Rate
Cardiac Output
O2Delivery
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Effects on RV
thoraxRA
RV
PA
positive
pressureventilation
Right Ventricular Filling
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PPV increases right atrial pressure
spontaneous breathing
RAP= mean systemic venous pressure
Right AtrialPressure
PSV
Systemic Venous Return
00
00 Max
Systemic Venous Return
RV Preload
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How does increasing PEEP affect PVR?
A. Increases PVR
B. Decreases PVR
C. Either is possible
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Lung VolumeLung Volume
PVRPVR
Large VesselsLarge Vessels
AtelectasisAtelectasis
Effect of Lung Volume on PVR
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Lung VolumeLung Volume
PVRPVR
Small VesselsSmall Vessels
AtelectasisAtelectasis
OverexpansionOverexpansion
Effect of Lung Volume on PVR
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Lung VolumeLung Volume
PVRPVRTotal PVRTotal PVR
Effect of Lung Volume on PVR
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5)PVR
(d-sec/cm
Cheifetz. CCM. 1998.
1000
1500
2000
2500
3000
3500
4000
4500
5000
10 15 20
PEEP 5 PEEP 10
Tidal Volume (mL/kg)
Overdistention and PVR
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CardiacOutput
(mL/min)
Cheifetz. CCM. 1998.
500
550
600
650
700
750
800
850900
950
1000
10 15 20
PEEP 5 PEEP 10
Tidal Volume (mL/kg)
Overdistention and PVR
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0
100
200
300
400
500
600
0 5 10 15 20 25
PaO2 vs. PEEP
Pa
O2(torr)
PEEP (cm H2O)
overdistend
collapse
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Cardiac Output vs. PEEP
2
2.5
3
3.5
4
4.5
5
5.5
0 5 10 15 20 25
PEEP (cm H2O)PEEP (cm H2O)
overdistend
collapse
CO
(l/min)
CO
(l/min)
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DO2 vs. PEEP
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0
100
200
300
400
500
600
0 5 10 15 20 25
0
100
200
300
400
500
600
0 5 10 15 20 25
PaO2 vs. PEEPPaO2 vs. PEEP
DO2 vs. PEEPDO2 vs. PEEP
Optimize O2 delivery
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Setting the Ventilator
Ventilator-InducedLung Injury
Gas Exchange
Patient Comfort Hemodynamics
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20 yo female with ALL
Immunosuppressed lastChemoTx 10 days ago
Adenoviral pneumonia
Febrile and pancytopenic (WBC2K; hematocrit 25; platelets 89K)
Intubated for severe hypoxemia
with tachypnea and dyspnea Vent: PCV, PIP 32 cm H2O,
VT 6 mL/kg PBW, I:E 1:2, PEEP14 cm H2O, rate 26, FiO2 0.60
ABG: pH 7.41, PaCO2 41 torr,PaO2 64 torr
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The goal of PEEP in this patient is to:
A. Increase PaO2
B. Decrease FiO2
C. Decrease risk of VILI
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Setting the Ventilator
Ventilator-InducedLung Injury
Gas Exchange
Patient Comfort Hemodynamics