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PEEP:Bring the Evidence to the Bedside
1. PEEP: Bringing the Evidence
to the Bedside
Ira M. Cheifetz MD FAARC
Duke Children's Hospital
Durham, NC
Dean R. Hess PhD RRT FAARC
Massachusetts General Hospital
Harvard Medical School
Boston, MA
2. 19 yo female with Crohn’s Disease
Immunosuppressed (once daily
6-mercaptopurine 100 mg po)
CMV pneumonia and diffuse
alveolar hemorrhage by BAL
Febrile and pancytopenic (WBC
2,000; hematocrit 26.2%;
reticulocytes 7.1%; platelets
89,000)
Intubated for severe hypoxemia
with tachypnea and dyspnea
Ventilator: VCV, VT 250 mL
(≈6 mL/kg PBW), I:E 1:2, rate
26/min, PEEP 14 cm H2O, FiO2
0.6
ABG: pH 7.41, PaCO2 41 mm Hg,
PaO2 64 mm Hg
3.
4. The goal of PEEP in this patient is to:
A. increase PaO2
B. decrease FiO2
C. decrease risk of VILI
5. Preventing Overdistention and
Collapse Injury
‘Lung Protective’ Ventilation
Add PEEP
Add PEEP
V
O
L
U
M
Limit Distending Pressure
Limit Vt
E
Pressure
6. Few topics generate more controversy!
What is the role of PEEP in 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 your
patient?
7. Edema in Rat Lungs After Ventilation
14/0 45/10 45/0
Webb HH et al. Am Rev Respir Dis. 1974;110:556-565.
9. Zone of
Overdistention
ion
lat
ha
Ex
tion
i ra
p
Ins
Ideal
PEEP
Zone of
Atelectasis
10. Studies have reported reduced mortality
with higher levels of PEEP when
compared to lower levels of PEEP.
A. True
B. False
11. 53 patients assigned to conventional or protective
mechanical ventilation.
Conventional ventilation: lowest PEEP for acceptable
oxygenation and VT 12 mL/kg.
Protective ventilation: PEEP above the lower
inflection point on the PV curve, VT < 6 mL/kg per
kilogram, recruitment maneuvers, PCV.
28 day mortality of 38% in the protective-ventilation
group and 71% the conventional-ventilation group (P
< .001).
N Engl J Med 1998;338:347
12. Control group (n = 50): VT 9–11 mL/kg PBW, PEEP
>5 cm H2O
Pflex/LTV group (n = 53): VT 5–8 mL/kg PBW and
PEEP at Pflex + 2 cm H2O
ICU mortality 32% in Pflex/LTV group versus 53% in
control group versus (P = .04)
Crit Care Med 2006; 34:1311
13. Was the mortality difference in the
Amato and Villar trials due to a lower
tidal volume, higher PEEP, or both?
A. Lower tidal volume only
B. Higher PEEP only
C. Combined effect of PEEP and tidal
volume
D. Who knows?
14. 861 patients with ALI/ARDS at 10 centers
randomized to VT 12 mL/kg PBW or 6
mL/kg PBW (VCV, Pplat ≤ 30 cm H2O)
25% reduction in mortality in patients
receiving smaller tidal volume
Number-needed-to-treat: 12 patients
N Engl J Med 2000; 342:1301
15. ALVEOLI (Assessment of Low tidal Volume and
elevated End-expiratory volume to Obviate Lung Injury)
2 PEEP levels with VT 6 mL/kg PBW
Oxygenation and respiratory system
compliance better with higher PEEP
Stopped at 549 patients for futility
No safety concerns
N Engl J Med 2004;351:327
16. Target tidal volume 6 mL/kg PBW
Control (n=508): Pplat ≤ 30 cm H2O (VCV), lower PEEP
Experimental (n=475): Pplat ≤ 40 cm H2O (PCV),
recruitment maneuvers (40 s at 40 cm H2O), initial
PEEP 20 cm H2O; higher PEEP
No significant difference in hospital mortality, but
improved secondary end points related to hypoxemia
and use of rescue therapies
Meade, JAMA 2008;299:637
17. Target tidal volume 6 mL/kg PBW
Control (n=382): low PEEP (5 - 9 cm H2O)
minimal distension strategy
Experimental (n=385): PEEP set to reach Pplat of
28 - 30 cm H2O (increased recruitment strategy);
PEEP 16 ± 3 cm H2O on day 1
No significant difference in mortality, but
improved lung function, reduced duration of
mechanical ventilation and duration of organ
failure
Mercat, JAMA 2008;299:646
18. 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 of PEEP
E. who knows?
19. Benefit of Higher PEEP Offset by Higher Pplat?
PPlat or PEEP (cm H20)
6 mL/kg
Non-
6 mL/kg
recruitable
Recruitable
(↑Crs, ↓Vd)
6
mL/kg
Injury Benefit
> >
Benefit Injury
Lower Higher
PEEP PEEP
20. 68 patients with ALI/ARDS underwent CT at airway
pressures of 5, 15, and 45 cm H2O.
Potentially recruitable lung varied
On average, 24% of the lung could not be recruited.
Patients with a higher percentage of potentially
recruitable lung had poorer oxygenation and
respiratory-system compliance, and higher levels of
dead space
N Engl J Med 2006;354:1775
23. Which is the best way to select PEEP?
A. PV curve
B. best compliance
C. PEEP/FiO2 table
D. stress index
E. who knows?
24. Optimal PEEP by Compliance
15 normovolemic patients requiring
mechanical ventilation for ARF
PEEP resulting in maximum oxygen
transport and the lowest dead-space
fraction resulted in highest compliance
Optimal PEEP varied from 0 to 15 cm H2O
Mixed venous PO2 increased from 0 PEEP
to the PEEP resulting in maximum oxygen
transport, but then decreased at higher
PEEP
Conclusion: compliance may be used to
indicate the PEEP likely to result in
optimum cardiopulmonary function
↑ PEEP
Suter, N Engl J Med 1975;292:284
25. Pressure-Volume Curve
1.6
normal
volume above FRC (liters)
1.2
ARDS
0.8
upper inflection
point
0.4
lower inflection
point
0
0 10 20 30 40
airway pressure (cm H2O)
28. Issues With PV Curves
Requires sedation/paralysis
Difficult to identify “inflection points” (Harris et al,
AJRCCM 2000; 161:432)
May require esophageal pressure to separate lung
from chest wall effects (Mergoni et al, AJRCCM 1997; 156:846
Ranieri et al, AJRCCM 1997; 156:1082)
Deflation limb may be more useful than inflation
limb (Holzapfel et al, Crit Care Med 1983;11:561; Hickling,
AJRCCM 2001;163:69)
Pressure-volume curves of individual lung units not
known (Hickling, AJRCCM 1998;158:194)
Role of PV curve for setting PEEP currently unknown
29. Decremental PEEP Trail
Theoretically attractive, but unproven
Hickling, AJRCCM 2001;163:69 Richard, Critical Care 2004, 8:163
31. AJRCCM 2007;176:761
In all 15 patients, the stress
index revealed hyperinflation
with the ARDSnet PEEP
strategy
PEEP decreased to normalize
the stress index
Compliance higher and plasma
cytokines lower using the stress
index compared with ARDSnet
36. 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 of
prevention of ventilator-induced lung injury
The benefit of precise setting of PEEP is
unproven
37. PEEP adversely affects cardiac output by
which of the following?
A. Decreased RV preload
B. Increased RV preload
C. Increased LV afterload
D. Decreased LV afterload
E. None of the above
38. 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)
53. Ventilator-Induced
Gas Exchange
Lung Injury
Setting the Ventilator
Patient Comfort Hemodynamics
54. 20 yo female with ALL
Immunosuppressed – last
ChemoTx 10 days ago
Adenoviral pneumonia
Febrile and pancytopenic (WBC
2K; 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, PEEP
14 cm H2O, rate 26, FiO2 0.6
ABG: pH 7.41, PaCO2 41 mm Hg,
PaO2 64 mm Hg
55.
56. The goal of PEEP in this patient is to:
A. increase PaO2
B. decrease FiO2
C. decrease risk of VILI
D. provide a good excuse for a 90 min
lecture
57. Ventilator-Induced
Gas Exchange
Lung Injury
Setting the Ventilator
Patient Comfort Hemodynamics
