Hess, PEEP
1
normal
lungs
20 min of
45 cm H2O
5 min of
45 cm H2O
How Do I ... PEEP?
Dean R. Hess PhD RRT FAARC
Assistant Director of Respiratory Care
Massachusetts General Hospital
Associate Professor of Anesthesia
Harvard Medical School
Editor in Chief
Respiratory Care
Dreyfuss, Am J Respir Crit Care Med 1998;157:294-323
ALI/ARDS
ALI/ARDS is Inhomogeneous
Avoid over-distention
(limit tidal volume and
plateau pressure)
Normal
Edema
Consolidation
Atelectasis
(Baby Lung)
Over-Distention
Avoid de-recruitment
(adequate PEEP)
Opening/Closing
ARDS Network Study
  861 patients with ALI/ARDS
VT 6 mL/kg
  Patients randomized to tidal volumes of 12
mL/kg PBW or 6 mL/kg PBW (VCV, A/C,
Pplat ≤ 30 cm H2O)
  25% reduction in mortality in patients
receiving smaller tidal volume
  Number-needed-to-treat: 12 patients
Pplat 25 – 26 cm H2O
Pplat 28 – 30 cm H2O
Red: hyper-inflated
Blue: normally aerated
Yellow: poorly aerated
Green: non-aerated
Pplat 25 – 26 cm H2O
N Engl J Med 2000; 342:1301
Pplat 28 – 30 cm H2O
Am J Respir Crit Care Med 2007; 175:160
Hess, PEEP
2
Initial Ventilator Settings
Protocol to Limit Tidal Volume
  A team of intensivists and RTs designed a
* Interstitial lung disease, lung resection, severe pneumonia, edema
** Sepsis, aspiration, transfusions
§ With significant spontaneous respiratory effort, plateau pressure
underestimates over-distention
§ With a stiff chest wall, plateau pressure overestimates overdistention
£ To prevent atelectasis and maintain oxygenation
protocol to limit VT
  Maximum 10 mL/kg in all patients
  6 - 8 mL/kg for patients at risk of ALI
  Implemented with protocol to limit unnecessary
transfusions
  ALI/ARDS decreased from 28% to 10%
  ICU mortality decreased from 20% to 7%
Yilmaz, Crit Care Med 2007;35:1660
Shultz, Anesthesiology 2007;106:1226
ALI/ARDS is Inhomogeneous
Normal
Edema
Consolidation
Atelectasis
(Baby Lung)
Over-Distention
Opening/Closing
Higher PEEP
Lower Tidal Volume
Webb and Tierney, Am Rev Respir Dis 1974;110:556
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 compliance better with
higher PEEP
  Stopped at 549 patients for futility: no
mortality difference
N Engl J Med 2004;351:327
  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 mortality difference, but improved secondary end
points related to hypoxemia and use of rescue therapies
Meade, JAMA 2008;299:637
Hess, PEEP
3
  Target tidal volume 6 mL/kg PBW
  Control (n=382): low PEEP (5 - 9 cm H2O) minimal
distension strategy
  Experimental (n=385): higher PEEP set to reach
Pplat of 28 - 30 cm H2O (increased recruitment
strategy); PEEP 16 ± 3 cm H2O on day 1
  No mortality difference, but improved lung function,
reduced duration of mechanical ventilation and
duration of organ failure
PPlat or PEEP (cm H2O)
Benefit of Higher PEEP Offset by
Higher Pplat?
6 mL/kg
Nonrecruitable
6
mL/kg
Injury
>
Benefit
6 mL/kg
Recruitable
(↑Crs, ↓Vd)
Benefit
>
Injury
Lower
PEEP
Higher
PEEP
Mercat, JAMA 2008;299:646
N = 2299
Briel, JAMA 2010;303:865
ARR: 4%
NNT: 25
N Engl J Med 2006;354:1775
How to Set PEEP
Optimal PEEP by Tidal Compliance
  PEEP/FIO2 tables per oxygenation
  15 normovolemic patients requiring
  Best compliance (lowest Pplat – PEEP)
  PEEP resulting in maximum oxygen transport
  Pressure-volume curve
  Lowest dead space
  Transpulmonary pressure (esophageal
balloon)
  Stress index
  Incremental vs. decremental?
mechanical ventilation for ARF
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
Titrate PEEP to lowest Pplat – PEEP
↑ PEEP
Suter, N Engl J Med 1975;292:284
Hess, PEEP
4
Pressure-Volume Curve
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
Stress Index
tidal recruitment
over-distention
PEEP = 8 cm H2O
SI = 0.75
Pplat = 20 cm H2O
Crs = 28 mL/cm H2O
PEEP= 18 cm H2O
SI = 0.97
Pplat = 28 cm H2O
Crs = 34 mL/ cm H2O
Grasso, AJRCCM 2007;176:761
Pulmonary vs. Extrapulmonary ARDS
(consolidation)
(atelectasis)
 PaO2
??? mortality
positive
transpulmonary
pressure
⎢ Ccw
Gattinoni, Am J Respir Crit Care Med 1998;158:3
N Engl J Med 2008;359:2095
Hess, PEEP
5
ALI/ARDS is Inhomogeneous
Setting PEEP for ALI/ARDS
  0 cm H2O: likely harmful
  8 – 16 cm H2O: appropriate in most patients
  Higher PEEP for ARDS; lower PEEP for ALI
  >20 cm H2O: seldom necessary
Normal
Edema
Consolidation
Atelectasis
  High PEEP should be reserved for cases where
recruitment can be demonstrated
(Baby Lung)
  PEEP should be selected in the context of prevention
Over-Distention
Opening/Closing
of ventilator-induced lung injury
  The benefit of “precise” PEEP is unproven
5 cm H2O PEEP
10 min after 0 PEEP
Cuff pressure 30 cm H2O
Crit Care Med 2008; 36:409
Crit Care Med 2008;36:2225
Hess, PEEP
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Positive End-Expiratory Pressure
PEEP
7 cm H2O
auto-PEEP
10 cm H2O
sensitivity
-1 cm H2O
auto-PEEP
3 cm H2O
sensitivity
-1 cm H2O
PEEP
10 cm H2O
PEEP
10 cm H2O
trigger effort = 11 cm H2O
trigger effort = 4 cm H2O
  Maintain alveolar recruitment
  Prevent ventilator-associated pneumonia
  Counterbalance auto-PEEP
  Reduce preload and afterload
  Splint airway with tracheomalacia
  Improve speech with tracheostomy cuff deflated
Although we can debate how it is precisely set ….
PEEP is good.