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How Should We Set PEEP?

Dean R. Hess

Disclosures

• Philips Respironics• Covidien

• Bayer• Jones and Bartlett

• McGraw-Hill• UpToDate• American Board of Internal Medicine

Webb and Tierney, Am Rev Respir Dis 1974;110:556

14/0 45/10 45/0

Higher PEEPLower Tidal Volume

Lower Driving Pressure

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Gattinoni, N Engl J Med 2006;354:1775

Stress Raiser

• There can be a 4 – 5 fold amplification of stress at the junction of an open and closed alveolus.

• This makes the case for improving the homogeneity in the lungs (alveolar recruitment) if it can be achieved safely.

• But if recruitment is not achieved, the stress in open alveoli will be very high during a recruitment maneuver and with high PEEP.

30 cm H2O

140 cm H2O

Mead et al, J Appl Physiol 1970;28:596

Stress Raiser

Concentration

of

Stress

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Recruitment Maneuvers

• An increase in airway pressure with the goal

to open collapsed lung tissue.

• A popular recruitment maneuver has been a

breath hold of 40 cm H2O for 40 seconds.

• Stepwise approaches are more effective than

abrupt applications of the high pressure, and

the graded rise of pressure is better tolerated

(Marini, Intensive Care Med 2011;37:1572).

0

5

10

15

20

25

30

35

40

PE

EP

an

d P

pla

t (c

m H

2O

)

FIO2: 1

VT: 0.3 L

ΔP: 15 cm H2O

SpO2: 79%

FIO2: 1

VT: 0.3 L

ΔP: 14 cm H2O

SpO2: 79%

FIO2: 1

VT: 0.3 L

ΔP: 13 cm H2O

SpO2: 80%

FIO2: 1

VT: 0.3 L

ΔP: 14 cm H2O

SpO2: 96% FIO2: 0.6

VT: 0.22 L

ΔP: 10 cm H2O

SpO2: 96%

Stepwise Recruitment Maneuver

Systematic Review And Meta-analysis

“The quality of the current evidence is low and insufficient in terms of allowing

for definitive and reliable conclusions. Thus, further research is likely to impact

our confidence in the estimate of the effect and may change the estimate.”

Suzumura, Intensive Care Med 2014;40:1227

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Are Recruitment Maneuvers Safe?

A 35-yr old male is admitted from an outside hospital for potential ECMO. He had abdominal surgery 3 wks prior for perforated bowel. He now has a PaO2 of 50 mm Hg on 100% O2 and 18 cm H2O PEEP. Would you do a recruitment maneuver?

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Higher vs. Lower PEEP

• VT 6 mL/kg PBW; 2 PEEP levels• ALVEOLI (Brower, N Engl J Med 2004;351:327)

– Oxygenation better with higher PEEP– Stopped early at 549 patients for futility

• LOVS (Meade, JAMA 2008;299:637)– Less hypoxemia and use of rescue therapies– No significant difference in hospital mortality

• EXPRESS (Mercat, JAMA 2008;299:646)– Improved lung function, reduced duration of

mechanical ventilation and organ failure– No significant difference in mortality

0

10

20

30

Lower PEEP

Higher PEEP

6 mL/kg

Ppl

at/P

EE

P (

cm H

2O)

6 mL/kg

6 mL/kg

Injury >

Benefit

Benefit >

Injury

Briel, JAMA 2010;303:865

Patients with moderate/severe ARDS Patients with mild ARDS

Individual patient meta-analysis of 3 negative RCTs.

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How to Set PEEP• Gas exchange

– Oxygenation: PEEP/FIO2 tables– Dead space

• Respiratory mechanics– Compliance (lowest driving pressure)– Pressure-volume curve– Stress index– Transpulmonary pressure (esophageal balloon)

• Imaging– Chest CT– EIT– Ultrasound

• Incremental vs. decremental?

Decremental PEEP Studies

Piraino, Respir Care 2013;58:886

Mild ARDS:

Moderate to Severe ARDS:

SpO2 88 – 95%

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Optimal PEEP by Tidal Compliance

Suter, N Engl J Med 1975;292:284

Titrate PEEP to lowest Pplat – PEEP

C = VT / (Pplat – PEEP)

Highest PEEP for Pplat 28 – 30 cm H2O

Mercat, JAMA 2008;299:646

ΔP = Pplat - PEEP

Amato, N Engl J Med 2015;372:747

Pressure-Volume Curve

Hess, Essentials of Mechanical Ventilation

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Pressure-Volume Curve

Hess, Essentials of Mechanical Ventilation

Respir Care 2011;56:514

Issues With PV Curves

• Requires sedation/paralysis• Difficult to identify inflection points• May require esophageal pressure to

separate lung from chest wall effects• Deflation limb may be more useful than

inflation limb • Pressure-volume curves of individual lung

units not known

Role of PV curve for setting PEEP currently unknown

Stress Index

Grasso, AJRCCM 2007;176:761

tidal recruitment over-distention

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PEEP= 18 cm H2OSI = 0.97Pplat = 28 cm H2O

PEEP = 8 cm H2OSI = 0.75Pplat = 20 cm H2O

PEEP = 10 cm H2OSI = 1.38Pplat = 35 cm H2O

PEEP= 0 cm H2O SI = 1.06 Pplat = 15 cm H2O

38

31

Direct vs. Indirect ARDS

Gattinoni, Am J Respir Crit Care Med 1998;158:3

(consolidation) (atelectasis)

� Ccw

E = 1/C

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49 year old male, acute pancreatitis, transferred from outside

hospital for ECMO due to hypoxemic respiratory failure. Firm

abdomen. Bladder pressure 21 mm Hg (28 cm H2O).

PEEP 28 cm H2O

Transpulmnary Pressure

3 cm H2O

SpO2 98%, FIO2 weaned to 0.4, PaO2 76 mm Hg

Transpulmonary pressure (stress): 10 cm H2O

Stress Index

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Chiumello, Crit Care Med 2014;42:252

Acute Pancreatitis, abdominal hypertension, sepsispH 7.20, PaCO2 57 mm Hg , PaO2 69 mm HgVT 450 mL (7 mL/kg IBW)FIO2 1, PEEP increased to 22 cm H2O

Ptp exp: 2 cm H2O

Pplat: 40 cm H2O

Stress: 17 cm H2O

PEEP 22 cm H2O

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Airway SI 1.14 Transpulmonary SI 1.18

• “Best PEEP” does not exist.

• “Better PEEP” as a reasonable compromise

among oxygenation, hemodynamic status, and

intra-tidal opening and closing.

– 15 - 20 cm H2O in severe ARDS

– 10 - 15 cm H2O in moderate ARDS

– 5 - 10 cm H2O in mild ARDS

Curr Opin Crit Care 2015, 21:50

Benefits of PEEP

• Maintain alveolar recruitment

• Counterbalance auto-PEEP

• Reduce preload and afterload

• Splint airway with tracheomalacia

• Prevent ventilator-associated pneumonia

• Speech with tracheostomy cuff deflated

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sensitivity-1 cm H2O

auto-PEEP10 cm H2O

trigger effort = 11 cm H2O

sensitivity-1 cm H2O

auto-PEEP2 cm H2O

trigger effort = 3 cm H2O

PEEP8 cm H2O

PEEP10 cm H2O

• Increase PEEP until there are no missed triggers• Increase PEEP until Pplat and PIP increase

PEEP to counterbalance auto-PEEP is only effective in the context of flow limitation; e.g., COPD versus asthm a

PEEP10 cm H2O

PEEP10 cm H2O

Belly Push

0 2 4 6 8 10

Pre

ssur

e (c

m H

2O)

F

low

(L

/min

)

time (s)

Pre

ssu

re (c

m H

2O)

F

low

(L/m

in)

time (s)

0 cm H2O PEEP

8 cm H2O PEEP

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PEEP is good!

… But must be used wisely!!