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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