Dissecting VILI from ARDS - Critical Care · PDF fileDissecting VILI from ARDS Luciano...
Transcript of Dissecting VILI from ARDS - Critical Care · PDF fileDissecting VILI from ARDS Luciano...
Dissecting VILI from ARDS
Luciano Gattinoni, MD, FRCP
Università di Milano
Fondazione IRCCS Ca’ Granda
Ospedale Maggiore Policlinico
Milan, Italy
2013, Toronto
Collagen and Elastin
1000
50
ST
RE
SS
(K
Pa)
STRAIN (%)
40 80
Elastin 10%
Collagen 2%
If empty zone (air)
to full zone ratio 100:1
Stress failure
100cmH2O
Collagen fiber network in rat lung
Collapsed Inflated AE =alveolar entrances
(scale bar 100 μm)
Toshima et al. Arch Histol Cytol. 67(1):31-40 (2004)
Time course of ventilator induced lung injury
Protti A. et al. Am J Respir Crit Care Med. 2011 Feb 4.
Hours of mechanical ventilation
0 12 24 36 48 60
L
un
g W
eig
ht
(g)
-200
-100
0
100
200
300
400
500
600
Str
ain
(V
t/F
RC
)
0.5
1.0
1.5
2.0
2.5
3.0
Strain (dVgas/Vgas0)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Str
ess
(PL
, cm
H2
O)
0
5
10
15
20
25
30
35
40
45
50
55
Stress-strain curve of healthy pigs
Specific Lung
Elastance
5.8 cmH2O
Protti A. et al. Am J Respir Crit Care Med. 2011 Feb 4.
VT/Kg (mL)
0 5 10 15 20 25 30 35 40 45 50
0
10
20
30
40
50
60
70
80
90
100
110
120
man
rat
rabbit mouse
Mercer RR. Et al. J Appl Physiol 1994 Sep;77(3):1060-66
Str
ain
in
dex
at
10m
L/K
g
1
2.13
3.08 3.18
Transpulmonary pressure (PL cmH2O)
0 4 8 12 16 20 24 28 32 36 40
40
50
60
70
80
90
100
%T
ota
l L
un
g C
ap
acit
y
0.0
1.0
2.0
Resting Biotrauma Stress at rupture
Agostoni, Mead,
Weibel,
Gattinoni
Specific Lung Elastance
12 (cmH2O)
1.5
0.5
Strain
1 2 3
V V
V V
Lung expansion/gas-free state
STRESS RISER=(10/1)2/3 = 4.64
10
1
Mead J J Appl Physiol. 1970 May;28(5):596-608.
Voxel
Vgas
Weighted gas ratio = Vgas1/Vgas0 * fraction of tissue
Gas fraction = Vgas0/Vvoxel
Mild
(N=82)
Moderate
(N=71)
Severe
(N=12) P
Dishomogeneity 1.49 ± 0.17 1.58 ± 0.29 1.75 ± 0.41 0.03
Extent 0.3 ± 0.1 0.36 ± 0.16 0.46 ± 0.18 0.01
Intensity 2.69 ± 0.27 2.76 ± 0.27 2.84 ± 0.41 0.31
Courtesy of Dr. Cressoni
Lung dishomogeneity and ARDS
Dishomogeneity2/3 1.30 ± 0.31 1.36 ± 0.44 1.45 ± 0.55
Intensity2/3 1.93 ± 0.42 1.97 ± 0.42 2.01 ± 0.55
Healthy subject
Moderate ARDS
Severe ARDS
Average ratio in normal subjects : 1.37±0.15
How do stress and
strain cause VILI?
Energy load into ventilatable
lung structures
Tidal Strain
P*ΔV = Energy Input
Dissipated Undissipated
Surface Tension
Sliding EM
Opening and Closing Elastic System
PEEP *ΔV = Energy Input = 0
Continuous Strain
TLC
FRC
Lun
g V
olu
me
VT 100%
VPEEP 0%
VT 75%
VPEEP 25%
VT 50%
VPEEP 50%
VT 25%
VPEEP 75%
Protti et al. Crit Care Med. 2013 Feb 4.
Vo
lum
e
Pressure
Volume-Pressure curve and energy (PΔV)
Recovered
Dissipated
Where is the
energy
dissipated?
Gas motion (resistance
etc.)
Extracellular sliding
(stress relaxation)
Surface tension
Opening/Closing
Degradation of 10% Vistanex 100 in cetane under laminar flow conditions. The
data show a linear decrease of molecular weight with increasing shear stress,
independent of the temperature. Reprinted with permission from ref 46.
Copyright 1959, American Chemical Society, Washington, DC.
Beyer MK, Clausen-Schaumann H. Chem Rev. 2005 Aug;105(8):2921-48.
Mechanical polymer fragmentation
O’Neill et al. Nature Medicine 11, 1161 - 1162 (2005)
Healthy Pig
Airway pressure (cmH2O)
0 5 10 15 20 25 30 35 40
Infl
ated
Volu
me
(mL
)
0
20
40
60
80
100
120
140
160
180
200
Dissipated Energy
1316 cmH2O*mL 1160 cmH2O*mL (-12%) 1478 cmH2O*mL (+12%) 1960 cmH2O*mL (+49%)
Constant VT, different PEEP
Airway pressure (cmH2O)
0 5 10 15 20 25 30 35 40
Infl
ated
Volu
me
(mL
)
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
0 cmH2O PEEP
5 cmH2O PEEP
10 cmH2O PEEP
13 cmH2O PEEP
ARDS
PEEP (cmH2O)
0 5 10 15D
issi
pat
ed E
ner
gy (
cmH
2O
*m
L)
1000
2000
3000
4000
5000
6000
7000
8000
Same plateau pressure, different PEEP
Strain
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
Nu
mb
er o
f p
igs
0
1
2
3
4
5
6
7
8
ZEEP ALIVE
ZEEP DEAD
PEEP ALIVE
PEEP DEAD
95% ALIVE ALL DEAD ≈50%
Protective effect of PEEP?
Conclusions
For VILI what matters is a tidal volume in a
ventilatable lung
Tidal strain ≥ 1.5 and total stress around 20 in man
are possible thresholds.
The stress risers allow to reach the threshold locally
and a moltiplication of pressure is nearly 2
PEEP does not produce energy load and its
positive effects may be due to the decraesed tidal
volume