Measuring end-expiratory
lung volume
Giacomo Bellani, M.D., Ph.D.
University of Milano-Bicocca
Monza, Italy
giacomo.bellani1@unimib.it
Conflicts of interest
Personal:
• Lecturing fees from GE
Institutional, research grants from:
• Draeger
• Maquet
• Chiesi Farmaceutici
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 @ 0 cmH2O= FRC
• How do we measure Endexpiratory lung volume?
• Why should we measure
end-expiratory lung volume?
Techniques
CT scan
• Precise quantitative assessment
• Radiological exposure+patient transfer
Closed circuit
• Need for a dedicated tracer+closed 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
Techniques
CT scan
• Precise quantitative assessment
• Radiological exposure+patient transfer
Closed circuit
• Need for a dedicated tracer+closed 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
Closed Dilution Technique
Ci
Vi
FRC
Mass
conservation
Cf
Vf
?
Vi* Ci = Vf* Cf
Vf = Vi + EELV
Ci
- Vi
EELV = Vi
Cf
Techniques
CT scan
• Precise quantitative assessment
• Radiological exposure+patient transfer
Closed circuit
• Need for a dedicated tracer+closed 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
FeN2
FiN2=70%
Vt
O2
30 %
600 ml
50 %
1000 ml
N2
70 %
1400 ml
50 %
1000 ml
400 ml N 2 400 ml

 2000 ml
0.7  0.5
0.2
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
Derives N2 concentration from:
100%- [CO2]- [CO2]
 Uses end-tidal concentration (no need for
synchronization)
What about Pressure Support ?
Using a 20% variation in FiO2:
4000
EELV by GE Engstrom (ml)
Volume Control
Pressure Support
3000
R2 = 0.8353
2000
1000
0
0
1000
2000
3000
4000
EELV by He dilution (ml)
Bellani G, unpublished
FRC INview (Engstrom carestation)
• How do we measure Endexpiratory lung volume?
• Why should we measure
end-expiratory lung volume?
Why should we measure endexpiratory lung volume?
EELV is profoundly reduced in ARDS
• Estimate of alveolar
recruitment
• Determinant of VILI
Why should we measure endexpiratory lung volume?
EELV is profoundly reduced in ARDS
• Estimate of alveolar
recruitment
• Determinant of VILI
Alveolar recruitment by P-V curve
Maggiore S. et al, Am J Resp Crit Care Med, 2001
Effect of recruitment on FRC (0 cmH2O)
Patroniti N et al., CCM 2010
Assessing
alveolar recruitment
A simplified
approach by EELV
Compliance=30 ml/cmH2O
EELV= 1000 ml
No recruitment
EELV= 1300 ml
Expected EELV increase:
30 * 10= 300 ml
PEEP = 0
Recruitment
EELV = 1600 ml
∆EELV / PEEP change = 600 / 6 = 100 ml/cmH2O
2
1950 l
1.8
1524 l
1.4
1350 ml
1.2
25
20
1
15
0.8
Crs 29 expected EELV increase 174 ml
0.6
10
true EELV increase 600 ml
0.4
5
0.2
0
0
4
6
8
10
12
PEEP (cmH2O)
14
Crs (ml/cmH2O)
30
1.6
EELV (l)
35
Why should we measure endexpiratory lung volume?
EELV is profoundly reduced in ARDS
• Estimate of alveolar
recruitment
• Determinant of VILI
SPECIFIC
HYPERVENTILATION
EELV
VE
(L/min)
RATIO
NORMAL
2500
<7
< 2.8
ARDS
1000
> 15
> 15
Vt/FRC
Regional distension and
inflammation
End-expiration
100
End-inspiration
EELVnormally-aerated
PET
High
activity
Kinormally-aerated
Vtnormally-aerated
-500
Low
activity
- 1000
Bellani G et al., Am J Resp Crit Care Med, 2011
The role of tidal volume/EELV
Bellani G et al., Am J Resp Crit Care Med, 2011
Conclusions:
o Measurement of end-expiratory lung volume is
now available:
RESEARCH TOOL → CLINICAL TOOL
o Useful in estimating lung recruitment
o Can it help in setting PEEP? Yes
o Is it being used to set PEEP? Don’t know
o Possible role in adjusting tidal volume?