Lung Protective Strategies: The Effects of Vt, PEEP

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Lung Protective StrategiesThe Effects of Vt,
PEEP Alveolar Recruitment

• David Grooms BS, RRT
• Sentara Norfolk General, Leigh Bayside Hospitals

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Understanding ARDS.2 Types

• Extrapulmonary ARDS (In-direct)

• Pulmonary ARDS (Direct)

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Identifying ARDS.2 Types?

• Extrapulmonary ARDS (In-direct)
• Multi-system Trauma
• Transfusion related ALI
• Acute pancreatitis
• Sepsis
• Post- CABG surgery
• Hemorrahagic shock

• Pulmonary ARDS (Direct)
• Pneumonia Bacterial or Viral
• Inhalation of noxious agent
• Aspiration of Gastric Contents
• Isolated pulmonary contusion
• Fat Embolus syndrome

Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
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Characteristics of Extrapulmonary ARDS
(In-direct)
Viera et al. Am J Respir Crit Care Med 1998158
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Contrasts between 2 types of ARDS
Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
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Characteristics of Extrapulmonary ARDS
(In-direct)
Viera et al. Am J Respir Crit Care Med 1998158
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Contrasts between 2 types of ARDS
Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
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Characteristics of Extrapulmonary ARDS
(In-direct)
Viera et al. Am J Respir Crit Care Med 1998158
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Contrasts between 2 types of ARDS
Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
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Characteristics of Extrapulmonary ARDS
(In-direct)
Viera et al. Am J Respir Crit Care Med 1998158
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Contrasts between 2 types of ARDS
Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
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Characteristics of Pulmonary ARDS (Direct)
Viera et al. Am J Respir Crit Care Med 1998158
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Contrasts between 2 types of ARDS
Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
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Characteristics of Pulmonary ARDS (Direct)
Viera et al. Am J Respir Crit Care Med 1998158
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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ARDS CT and PV Curve (slow inflation)
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Contrasts between 2 types of ARDS
Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
71
Characteristics of Pulmonary ARDS (Direct)
Viera et al. Am J Respir Crit Care Med 1998158
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Contrasts between 2 types of ARDS
Kallet, R Branson, R. Resp. Care Journal, Apr
2007, Vol 52 No 4
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Characteristics of Pulmonary ARDS (Direct)
Viera et al. Am J Respir Crit Care Med 1998158
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Effects of Mechanical/Physical Stretch on Rat
Alveolar Epithelial Cells

• Tschumperlin, D et al. Am J Respir Crit Care Med,
  Vol 162. pp 357-362, 2000
• Excised Rat lungs
• Placed Alveolar Epithelial Cells in a
  cell-stretching device

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Tschumperlin, D et al. Am J Respir Crit Care Med,
Vol 162. pp 357-362, 2000
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Tschumperlin, D et al. Am J Respir Crit Care Med,
Vol 162. pp 357-362, 2000
Both static and single deformations were
significantly less injurious than cyclic
deformations at each deformation level
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Tschumperlin, D et al. Am J Respir Crit Care Med,
Vol 162. pp 357-362, 2000
Cell Death dependent on frequency
Reducing the amplitude reduced cell death
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ARDS Network
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ARDS Network

• Multicenter, Randomized trial
• 861 Patients recruited from March 1996 through
  March 1999 at 10 university centers.
• Patients enrolled if
• 1) They were receiving mechanical ventilation
• 2) Had acute decrease in the P/F ratio (lt300)
• 3) Bilateral pulmonary infiltrates on a chest
  radiograph consistent with the presence of edema
• 4) No clinical evidence of left atrial
  hypertension or if measure a PCWPlt18mmHg.

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Results

• Trial was stopped after fourth interim analysis.
• Mortality rates
• 12 cc/Kg VT group- 39.8
• 6cc/Kg Vt group- 31.0
• Mortality decreased by 22
• Vt Plat were significantly lower
• Question to you-
• What group had better PaO2s?
• 12 they died more often- so better PaO2 does
  not translate into better outcomes

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What did we do then?

• We were skeptical at the results. Didnt like it
  because Vt was so low.
• Also questioned that mortality could have been
  better if more PEEP was used or use of
  Recruitment Maneuvers.
• Did we interpret the results of the studies
  right???

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Target enrollment- 750 ALI, ARDS pts.
Lower PEEP/Higher FiO2 FiO2 .3 .4 .4 .5
.5 .6 .7 .7 .7 .8 .9 .9 .9
1.0 PEEP 5 5 8 8 10 10 10 12 14 14
14 16 18 18-24 Higher PEEP/Lower FiO2 FiO2
.3 .3 .4 .4 .5 .5
.5-.8 .8 .9 1.0 PEEP
12 14 14 16 16 18 20 22 22 22-24
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Recruitment Maneuver Attempts

• RMs were performed on the first 80 patients
  assigned to the higher PEEP group.
• 1 or 2 manuevers per day _at_ 35-40cmH2O for 30
  seconds.
• Mean increase in O2sat was small transient.
  Therefore RM were DCd for the remainder of the
  trial.

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Results

• Trial stopped _at_ the 2nd interim analysis after
  549 pts. Had been enrolled.
• Stopped based on the specified futility stopping
  rule.
• Surprising Results

ESSENTIALLY NO DIFFERENCE IN OUTCOMES (MORTALITY)
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Interpretation..

• PEEP does not improve mortality of ARDS patients.
  
• Added to our own confusion
• Now what do we do if PEEP doesnt help survival
• Instead of developing my own interpretation of
  the results, I will wait around until someone
  shows me the right way to do it.
• Do our dirty work for us!!!

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So what can we do to try to do it right??

• Question aspects of personal satisfaction vs.
  patient overall satisfaction

I got the PaO2 up from 70-80 by turning the Vt up
to 1200cc. You know I am the man right?
Wow, awesome job, I will try to get it higher
than you did today! You are the man
VS
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So what can we do to try to do it right??

• Example Patient with ALI/ARDS
• Steps to take to minimize progression of syndrome
• Minimize FIO2, make all attempts to decrease FIO2
  lt60.

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Oxygen Dissociation Curve
ARDSnet Study 88-94 PaO2 55-80
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So what can we do to try to do it right??

• Example Patient with ALI/ARDS
• Steps to minimize progression of disease/syndrome
• Minimize FIO2, make all attempts to decrease FIO2
  lt60.
• Management and consideration of Vt

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Can mechanical ventilation actually produce lung
injury?

• Webb Tierney, 1974, Am Rev Respir Dis
  110556-565

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Key Findings of the study

• Healthy Lungs with low PIP does not cause lung
  injury
• Ventilation with high PIP (30-45) no PEEP
  produces perivascular edema leads to severe
  injury.
• PEEP provides protection from alveolar edema due
  to high PIP.

• Webb Tierney, 1974, Am Rev Respir Dis
• 110556-565

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Overdistention/Increased Transalveolar Pressure
of Good alveoli
Nieman, G
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Take Home

• Minimize Stretching of Healthy Alveoli by
  reducing Vt or Plat pressure.
• OK but what about patients that do not have
  ALI/ARDS??

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Crit Care Med 2004 Vol. 32, No. 9
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Results

• VTs above 9cc/Kg cause VILI in non- ARDS
  patients.
• The incidence of
• VILI is higher in pts.
• who get gt9cc/Kg
• VT. blood transfusions.

What if I go too low on the Vt because I am
trying to protect?
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Pt. Placed on 6cc/Kg Vt
SNGH Burn/Trauma Unit
Pt. Placed on 6cc/Kg Vt
Pt. Switched To AVTS Mode. Maintained _at_
8-9ccs/Kg
Pt. Placed on 8-9cc/Kg Vt
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So what can we do to try to do it right??

• Example Patient with ALI/ARDS
• Steps to take to minimize progression of syndrome
• Minimize FIO2, make all attempts to decrease FIO2
  lt60.
• Management and consideration of Vt
• Management of PEEP

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How to set PEEP

• Use PEEP FIO2 table from ARDSnet study
• FiO2 .3 .4 .4 .5 .5 .6 .7 .7 .7
  .8 .9 .9 .9 1.0
• PEEP 5 5 8 8 10 10 10 12 14 14 14
  16 18 18-24
• This table is designed to be appropriate for the
  average patient, but sometimes PEEP needs to be
  individualized

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How to set PEEP

• Use PEEP FIO2 table from ARDSnet study
• Set PEEP based off Lower Inflection point (pflex)

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Rimensberger P et al. CCM 1999271940-1945
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Crit Care Med 2006 Vol. 34, No. 5
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Amato, M. et al. 1998. NEJM
Villar, et al. Crit Care Med 2006 Vol. 34, No. 5
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Minimizing Atelectatictrauma(repeated opening
and closing)
Nieman, G.
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How to manage PEEP

• Use PEEP FIO2 table from ARDSnet study
• Set PEEP based off Lower Inflection point (pflex)
  1-2cm
• Set PEEP based off Point of maximum Curvature or
  recruitable lung volume via deflation limb of PV
  curve

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The Effects of Recruitment on End-expiratory Lung
Volume
APRV/HFOV puts pt. at this point
Barbas CSV Am J Respir Crit Care Med 2002165A218
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Hickling K. AJRCCM 200116369-78.

APRV/HFOV puts pt. at this point
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Rimensberger P et al. CCM 1999271940-1945
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350 ccs
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Maximizing a current modality

• Not how much but HOW!
• Pressure Modes Use of Flow Time pattern for
  adequate inspiratory phase to improve gas
  distribution and minimize level of pressure
  needed for ventilation

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I-times in Pressure Modes for Full Flow
deceleration improve gas distribution and
minimize PC level
F
Vt
Vt
T
P
MAP
MAP
T
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I-times in Pressure Modes for Full Flow
deceleration improve gas distribution and
minimize PC level
F
Vt
Vt
T
P
MAP
T
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I-times in Pressure Modes for Full Flow
deceleration improve gas distribution and
minimize PC level
F
Vt
Vt
Vt
T
Min.Insp. Pressure Adjustments Needed
P
MAP
T
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Maximizing a current or alternative modality

• Not how much but HOW!
• Pressure Modes Use of Flow Time pattern for
  adequate inspiratory phase to improve gas
  distribution and minimize level of pressure
  needed for ventilation
• Use of Airway Pressure Release Ventilation
  (APRV), HFOV, Jet Ventilation

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Normal Ventilation with Normal MAP
P
Peak
Insp
Plat
20
15
5
PEEP
PEEP
Mean Insp Pressure
Mean Exp Pressure


MAP
Time
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Increase in Insp. PressureWhat will happen to
MAP?
P
Insp
25
Peak
Plat
20
15
5
PEEP
PEEP
Mean Insp Pressure
Mean Exp Pressure


MAP
Time
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Increase in Insp. PressureWhat will happen to
Plat?
P
Insp
Plat
25
Peak
20
15
5
PEEP
PEEP
Mean Insp Pressure
Mean Exp Pressure


MAP
Time
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Increase in PEEP, What will happen to MAP Plat?
P
Insp
Peak
Plat
20
15
10
5
PEEP
PEEP
Mean Insp Pressure
Mean Exp Pressure


MAP
Time
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APRV (Basically inverse Ratio with Spont.
Breathing during insp. Phase.) Can Increase MAP
and keep safe Plat. spont. Breath.
P
If Flow is Fully dec.
Spontaneous Breaths

Plat
Peak
Insp
20
15
5
PEEP
PEEP
Mean Insp Pressure
Mean Exp Pressure


MAP
Time
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Summary

• Understand disease type, what is cause for
  inflammation of the Lung
• Manage FIO2 lt60 with PaO2 gt60mmHg SpO2 gt88
• Manage Vt (4-8cc/KgIBW) Plateau Pressure
  lt30cmH2O to minimize stretch on good and bad
  alveoli. gt9cc/Kg IBW in non ARDS patients
  increases incidence of ALI developement
• Commericial Vents actually incorporate an
  automatic Lung Protective Strategy (Hamilton
  Galileo/ASV Mode Drager Evita XL)

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Summary

• PEEP can be managed by multiple options, Goal is
  to prevent repeated alveolar opening and closing,
  and proper recruitment of dependent lung units
• Alternative Modes can improve specific indices,
  but lack appropriate randomized clinical trials
  for universal acceptance
• Optimize settings to improve gas distribution on
  conventional modes

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Thank Yall for having me!!