Measuring end-expiratory lung volume

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Measuring end-expiratory lung volume

• Giacomo Bellani, M.D., Ph.D.
• University of Milano-Bicocca
• Monza, Italy
• giacomo.bellani1_at_unimib.it

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Conflicts of interest

• Personal
• Lecturing fees from GE
• Institutional, research grants from
• Draeger
• Maquet
• Chiesi Farmaceutici

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Which lung volume ?
Functional Residual Capacity (FRC) Volume of gas
in the lung at the end of a physiologic
expiration Relaxation volume of respiratory
system
End Expiratory Lung Volume (EELV) Volume of gas
in the lung at end expiration during mechanical
ventilation with PEEP
EELV _at_ 0 cmH2O FRC
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How do we measure End-expiratory lung volume?

• Why should we measure end-expiratory lung volume?

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Techniques

• CT scan
• Precise quantitative assessment
• Radiological exposurepatient transfer
• Closed circuit
• Need for a dedicated tracerclosed system
• No need for fast response concentration
  measurements - offline measurement
• Open circuit muti-breath washin/washout
• Potentially no need for a gas tracer
• Fast response measurement, synchrony with tidal
  ventilation

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Techniques

• CT scan
• Precise quantitative assessment
• Radiological exposurepatient transfer
• Closed circuit
• Need for a dedicated tracerclosed system
• No need for fast response concentration
  measurements - offline measurement
• Open circuit muti-breath washin/washout
• Potentially no need for a gas tracer
• Fast response measurement, synchrony with tidal
  ventilation

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Closed Dilution Technique
Ci Vi
Cf Vf
Mass conservation
FRC ?
Vi Ci Vf Cf
Vf Vi EELV
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Techniques

• CT scan
• Precise quantitative assessment
• Radiological exposurepatient transfer
• Closed circuit
• Need for a dedicated tracerclosed system
• No need for fast response concentration
  measurements - offline measurement
• Open circuit muti-breath washin/washout
• Potentially no need for a gas tracer
• Fast response measurement, synchrony with tidal
  ventilation

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FeN2
FiN270
Vt
30
50
O2
600 ml
1000 ml
70
N2
50
1400 ml
1000 ml
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Multibreath nitrogen washout
Off-line correction of viscosity effect on
sidestream delay time and pneumothacografic
measurments
Wrigge H et al Intensive Care Med 1998 24 487
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• Derives N2 concentration from
• 100- CO2- CO2
• Uses end-tidal concentration (no need for
  synchronization)

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What about Pressure Support ?
Using a 20 variation in FiO2
4000
Volume Control
3000
EELV by GE Engstrom (ml)
2000
1000
0
0
1000
2000
3000
4000
EELV by He dilution (ml)
Bellani G, unpublished
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FRC INview (Engstrom carestation)
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How do we measure End-expiratory lung volume?

• Why should we measure end-expiratory lung volume?

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Why should we measure end-expiratory lung volume?
EELV is profoundly reduced in ARDS

• Estimate of alveolar recruitment
• Determinant of VILI

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Why should we measure end-expiratory lung volume?
EELV is profoundly reduced in ARDS

• Estimate of alveolar recruitment
• Determinant of VILI

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Alveolar recruitment by P-V curve
Maggiore S. et al, Am J Resp Crit Care Med, 2001
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Effect of recruitment on FRC (0 cmH2O)
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Patroniti N et al., CCM 2010
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Assessing alveolar recruitment by EELV
A simplified approach
No recruitment EELV 1300 ml
Compliance30 ml/cmH2O EELV 1000 ml
Expected EELV increase 30 10 300 ml
PEEP10
PEEP 0
Recruitment EELV 1600 ml
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?EELV / PEEP change 600 / 6 100 ml/cmH2O
2
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1.8
30
1.6
25
1.4
1350 ml
1.2
Crs (ml/cmH2O)
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EELV (l)
1
15
0.8
0.6
10
0.4
5
0.2
0
0
14
4
6
8
10
12
PEEP (cmH2O)
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Why should we measure end-expiratory lung volume?
EELV is profoundly reduced in ARDS

• Estimate of alveolar recruitment
• Determinant of VILI

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SPECIFIC HYPERVENTILATION



EELV
VE (L/min)
RATIO
NORMAL
2500
lt 7
lt 2.8
ARDS
1000
gt 15
gt 15
30
Vt/FRC
31
Regional distension and inflammation
End-expiration
End-inspiration
PET
High activity
100
Kinormally-aerated
EELVnormally-aerated
Vtnormally-aerated
-500
Low activity
- 1000
Bellani G et al., Am J Resp Crit Care Med, 2011
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The role of tidal volume/EELV
Bellani G et al., Am J Resp Crit Care Med, 2011
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Conclusions

• Measurement of end-expiratory lung volume is now
  available
• RESEARCH TOOL ? CLINICAL TOOL
• Useful in estimating lung recruitment
• Can it help in setting PEEP? Yes
• Is it being used to set PEEP? Dont know
• Possible role in adjusting tidal volume?

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