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(Optimizing) CT scan in ARDS patients
Antonio Pesenti
Fondazione IRCCS Ospedale Maggiore Policlinico Università di Milano
Italy
Antalya 2016
CT scan in ARDS
Gattinoni L, Pesenti A. Intensive Care Med 2005
“CT dramatically changed our view of ARDS. What was considered a homogenous lung, as usually shown by antero-‐posterior
radiography,… ”
Pathologic conditions where the CT has been proven
clinically useful :
• Pleural effusion • Pneumothorax • Chest tube malpositioning • Lung abscess
Simon et al. Respiratory Care 2016
RESPIR CARE 2016
• 204 CTs included. The most common findings were:
• consolidations (94.1%) • ground glass opacities (85.3%). • pleural effusions (80.4%) • mediastinal lymphadenopathy (66.7%) • RV strain and pulmonary hypertension (54%) • pericardial effusion (37.3%), • emphysema of the chest wall (12.3%), • pneumothorax (11.8%), • emphysema of the mediastinum (7.4%), • pulmonary embolism (2.5%).
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RESPIR CARE 2016
• Intrahospital transport was associated with critical incidents in 8.3% of cases.
• CONCLUSIONS: Thoracic CT scans yielded information useful for diagnosis, prognosis, and recognizing concomitant disorders requiring therapeutic interventions.
• Results obtained from CT scans led to changes in
management in 26.5% of cases.
Simon et al. Respiratory Care 2016 PNEUMOCISTOSIS
CAP Simon et al. Respiratory Care 2016 ASPERGILLUS Simon et al. Respiratory Care 2016
Pirro 4 B
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CT scan
• improves diagnostic accuracy • precisely defines anatomic
abnormalities • affects treatment decisions
Adult Respiratory Distress Syndrome Due to Pulmonary and
Extrapulmonary Causes: CT, Clinical, and Functional
Correlations
Goodman et al. Radiology 1999;213:545-552
Goodman et al Radiology 1999 0
10
20
30
40
50
60
70
80
90
TD (gg+co) Tgg Tco
PRIMARY ARDS SECONDARY ARDS
RESULTS
p <0.05
Goodman et al Radiology 1999
CONCLUSIONS
Ground glass is predominant in secondary ARDS, consolidation in
primary ARDS.
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CT scan in ARDS • Morphological analysis
• Quantitative analysis
LOW PRESSURE
C T
n u m
b e r s
f r e q
u e n c
y ( %
)
50
10
40
30
20
0 -900 -800 -700 -600 -500 -400 -300 -200 -100 0 100
CT numbers (Hounsfield Units)
-1000
Hyp
erin
flate
d
Nor
mal
ly a
erat
ed
Poo
rly a
erat
ed
Non
aer
ated
Normal
ARDS
CT “density”
mass
volume
REF
CT
Normal
1000 g
1292 ± 198 g
ARF
> 2500 g
2589 ± 1201 g
LUNG WEIGHT
Low
High
ACTIVITY
CT D (HU) -1000 -800 -600 -400 -200 0 200
KiD
· 104 (m
l/min/m
l)
0
50
100
150
200
250
Regional distribution of 18FDG signal
Courtesy of Dr. Bellani
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CT Take Home Message 1
• In ARDS – No region of the lung is really healthy – The entire lung is “diseased” – No region of the lung is spared from
inflammation LIP
Best PEEP
IC
UIP
DC
UV
HA
Vol
ume
Pressure
Volume-Pressure curve
Gattinoni et al. Am Rev Respir Dis 1987;136:730-736
1.0
0.8
0.6
0.4
0.2
0
Nor
mal
ly a
erat
ed ti
ssue
[kg
]
0 10 20 30 40 50 C start [ml/cm H2O]
r = 0.83 p < 0.01
CT Take Home Message 2
• In ARDS – The lung is not stiff: – The lung is small ( the baby lung)
The concept of "baby lung". Gattinoni L, Pesenti A. Intensive Care Med. 2005 ;31:776.
Without gravity
Interstitial edema and increased mass
The Sponge Model
g/t - 0.6
g/t - 0.6
g/t - 0.6
With gravity
Superimposed Pressure
Interstitial edema, increased mass
and collapse
g/t - 0.2
g/t - 1.0
g/t - 0.5
SUPERIMPOSED PRESSURE cm H2O
Regional Effects and Mechanism of Positive End Expiratory Pressure in Early adult Respiratory Distress Syndrome
Gattinoni L et al JAMA. 1993 Apr 28;269(16):2122-7.
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CT Take Home Message # 3
• In ARDS – In early ARDS the lung weight itself
causes a dependent distribution of densities
What is recruitment?
• Opening of previously closed ( collapsed, atelectatic) airways
• Airways previously closed, that pop open at a pressure, and stay open at the pressure at which they were previuosly closed
• Opening of airways or opening of perfused airways?
What is recruitment?
• Opening of previously closed ( collapsed, atelectatic) airways
• Airways previously closed, that pop open at a pressure, and stay open at the pressure at which they were previuosly closed
• Opening of airways or opening of perfused airways?
Oleic acid in dog
20
40
60
80
100
Pressure [cmH2O] 10 20 30 40 60 50
Tot
al L
ung
Cap
acit
y [%
]
R = 22%
R = 81%
R = 100% R = 93%
0 0
R = 0%
R = 59%
Paw [cmH2O]
%
Opening and closing pressures
0 5 10 15 20 25 30 35 40 45 50 0
10
20
30
40
50
Opening pressure
Closing pressure
5 patients, ALI / ARDS
Crotti et al. Am J Respir Crit Care Med 2001; (In press)
Recruitment • Achieved by a opening pressure
(pressure high) • Maintained by a high enough PEEP
( low pressure)
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CT scan and recruitment
Gattinoni L et al. NEJM 2006
Potential of lung recruitment: difference in non-‐aerated lung tissue between high (45) and low (5) PEEP.
potential for lung recruitment [% total lung weight]
-10 -5 -5 0 0-5 5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60 60-65 65-70 70-75 75-80
Freq
uenc
y [n
o. o
f pat
ient
s]
0 2 4 6 8
10 12 14 16 18 20 22 24
Figure 1
ALI patients ARDS patients
higher
21 ± 10% (374 ± 236 grams)
lower
5 ± 4% (59 ± 51 grams)
L. Gattinoni, NEJM 2006
Potential for lung recruitment
mortality [%]
quartiles of potential for lung recruitment
1st 0
10
20
30
40
50
60
lower- potential
2nd 3rd 4th
Mortality at ICU-discharge
17 n = 17 17 17
higher- potential
P=0.006
L. Gattinoni, NEJM 2006
airway pressure [cmH2O]
Non-aerated tissue [gr]
0 5 10 15 20 25 30 35 40 45 50 200
300
400
500
600
700
800
900
140 gr
63 gr
20 gr
7 gr
inspiration expiration
Higher-potential Lower-potential
Opening and closing of alveoli
CT Take Home Message # 4
• In ARDS – PEEP is not recruiting pressure
– PEEP prevents the collapse of the recruited tissue
Intensive Care Med 2014 ; 40: 691
In patients with ARDS a 70 % effective dose reduction can be achieved without significant effect on quantitative and visual anatomical results
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CT Scan in ARDS: when?
• Early, to improve diagnosis, prognosis and therapeutic approach
• When something unexpected or unexplained happens
• Late to assess the evolution
Cressoni et al. Am J Respir Crit Care Med 2014
NORMAL MILD
MODERATE SEVERE
Cressoni et al. Am J Respir Crit Care Med 2014
Galiatsou:Am J Respir Crit Care Med. 2006;174:187 Galiatsou:Am J Respir Crit Care Med. 2006;174:187
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CT Take Home Message # 4
• Prone Positioning – In ARDS increases the homogeneity
of ventilation and aeration