Critical Care Radiology: The Role of Imaging in Acute Respiratory Distress
SyndromeAndrew Chalupka, MS III
Gillian Lieberman, MD
September, 2011
Andrew Chalupka, MS IIIGillian Lieberman, MD
Overview• Case presentation: index patient• Use of chest radiography to distinguish between causes of airspace
opacification
• Use of chest radiography to distinguish between cardiogenic
and non‐
cardiogenic
pulmonary edema• Acute Respiratory Distress Syndrome (ARDS):
– Definition– Associated disorders– Diagnostic criteria– Pathophysiology
• Imaging choices for ARDS• Radiologic findings in ARDS by stage• Implications of imaging for understanding ARDS pathophysiology• Implications of imaging for managing ARDS
2
Andrew Chalupka, MS IIIGillian Lieberman, MD
Index Patient: Brief History
• 33 year‐old man
• Two‐day history of “feeling unwell”• Day of admission: onset of “worst headache
of [his] life,”
followed by nausea and vomiting
• At outside hospital, CT showed extensive subarachnoid hemorrhage and
intraventricular
hemorrhage
3
Andrew Chalupka, MS IIIGillian Lieberman, MD
Index Patient: Brief Hospital Course
• Within an hour of arrival in the ED, becomes lethargic and is intubated
• Admitted to ICU• Week 1: Tachycardia, hypertension, and fever
– Therapeutic hypothermia protocol initiated
• Week 2: Pneumonia• Week 3: Extubated
dyspnea, rapid hypoxemia re‐intubated
4
Andrew Chalupka, MS IIIGillian Lieberman, MD
Index Patient
The patient’s chest radiograph follows.
It was taken 24 hours after the onset of his dyspnea
and hypoxemia.
Attempt to interpret the film independently,
then continue to view findings.
5
6Source: Beth Israel Deaconess
Medical Center PACS
Index Patient: Chest radiograph,24 hours after onset of respiratory distress
7Source: Beth Israel Deaconess
Medical Center PACS
Diffuse,
hazy
opacities
Index Patient: Chest radiograph
8Source: Beth Israel Deaconess
Medical Center PACS
Diffuse,
hazy
opacities
Index Patient: Chest radiograph
9Source: Beth Israel Deaconess
Medical Center PACS
Air bronchograms
Index Patient: Chest radiograph
10Source: Beth Israel Deaconess
Medical Center PACS
Diffuse,
hazy
opacities
Diffuse,
hazy
opacities
Air
bronchogram
s
Index Patient: Chest radiograph
Andrew Chalupka, MS IIIGillian Lieberman, MD
Given only a chest radiograph with an airspace/alveolar
pattern of opacification, what can we determine about its
etiology?
Quite a bit.
11
Andrew Chalupka, MS IIIGillian Lieberman, MD
Airspace OpacificationCause of Opacification Radiographic AppearanceCardiogenic pulmonary edema • Diffuse
• Symmetric• Perihilar• ±
Dependent
Non‐cardiogenic pulmonary edema(e.g., ARDS)
• Patchy• Asymmetric• Peripheral• ±
Dependent• ± Air bronchograms
Bronchopneumonia • Patchy• Asymmetric• Peripheral• Non‐dependent
Aspiration pneumonia • Patchy• Asymmetric• Dependent
Septic infarcts • Peripheral• Wedge‐shaped
12Adapted from: Trotman‐Dickenson B. Radiography for the Critical Care Patient. In: McLoud TC, Boiselle
PM, eds.
Thoracic Radiology: the Requisites. Philadelphia, PA: Mosby; 2010: 136‐159.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Our patient’s film showed airspace opacification that was diffuse, peripheral,
and worse at the bases (i.e., potentially dependent) with air bronchograms.
It demonstrates many, but not all, of the
common radiographic features of non‐cardiogenic pulmonary edema.
13
Andrew Chalupka, MS IIIGillian Lieberman, MD
Pulmonary Edema
• Abnormal accumulation of fluid in the extravascular compartments of the lung
• Net fluid movement = Kf
([Pc
– Pi
] –
σ[πc
–
πi
])
• Pathophysiologic categories of pulmonary edema:– increased hydrostatic pressure edema
– permeability edema with diffuse alveolar damage (DAD)
– permeability edema without DAD
– mixed edema
14Source: Ketai LH, Godwin JD. A new view of pulmonary edema and acute respiratory distress
syndrome. J Thorac Imaging. 1998;13(3):147‐71.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Having narrowed down the cause of our patient’s airspace opacification to
pulmonary edema, we can use the features of his chest radiograph to determine the type
of pulmonary edema.
The chest radiograph is a powerful tool in
the critical care setting; it can provide an assessment of volume status and vascular flow patterns.
15
Andrew Chalupka, MS IIIGillian Lieberman, MD
Radiographic Features of Pulmonary Edema: Cardiac vs. Non‐cardiac
Signs Cardiogenic Edema Fluid Overload ARDS
Cardiomegaly + +
Vascular redistribution +
Widened vascular pedicle + +
Pleural effusions + +
Kerley lines + +
Peribronchial cuffing + +
Airspace opacification Diffuse perihilar Central
perihilar
Patchy
peripheral
16Adapted from: Trotman‐Dickenson B. Radiography for the Critical Care Patient. In: McLoud TC, Boiselle
PM, eds.
Thoracic Radiology: the Requisites. Philadelphia, PA: Mosby; 2010: 136‐159.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Based on our patient’s clinical presentation, the airspace opacification pattern on his
chest radiograph, and the absence of CXR features seen in cardiogenic or fluid‐
overload pulmonary edema, we suspect that he has Acute Respiratory Distress
Syndrome (ARDS).
Let’s continue by briefly examining the etiology and pathophysiology of ARDS.
17
Andrew Chalupka, MS IIIGillian Lieberman, MD
ARDS: Definition and Associated Disorders• A clinical syndrome of abrupt‐onset dyspnea and
hypoxemia in the setting of diffuse pulmonary infiltrates• Disorders associated with ARDS:
18
Direct lung injury Indirect lung injury
Pneumonia Sepsis
Aspiration of gastric contents Shock
Pulmonary contusion Severe trauma
Drowning Multiple transfusions
Fat/amniotic fluid embolism Salicylate or narcotic overdose
Smoke/toxic gas inhalation Pancreatitis
Sources:Levy BD, Shapiro SD. Acute Respiratory Distress Syndrome. In: Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL,
Jameson JL, Loscalzo J, eds. Harrison's Principles of Internal Medicine
17e. New York, NY: McGraw Hill; 2008: 1680‐1684.Wheeler AP, Bernard GR. Acute lung injury and the acute respiratory distress syndrome: a clinical review. Lancet.
2007;369(9572):1553‐64.
Andrew Chalupka, MS IIIGillian Lieberman, MD
ARDS: Diagnostic Criteria1.
Acute onset (<7 days)
2.
PaO2
/FIO2
<200 mmHg• Acute Lung Injury: PaO2
/FIO2
<300 mmHg
3.
Diffuse, bilateral pulmonary infiltrates on frontal radiograph
4.
Absence of left atrial hypertension• PCWP <18 mmHg if measured, or• No clinical evidence of elevated LA pressure
19
Sources:Levy BD, Shapiro SD. Acute Respiratory Distress Syndrome. In: Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL,
Jameson JL, Loscalzo J, eds. Harrison's Principles of Internal Medicine
17e. New York, NY: McGraw Hill; 2008: 1680‐1684.Wheeler AP, Bernard GR. Acute lung injury and the acute respiratory distress syndrome: a clinical review. Lancet.
2007;369(9572):1553‐64.
Andrew Chalupka, MS IIIGillian Lieberman, MD
ARDS: Pathophysiology• Alveolar capillary membrane: 2 separate barriers
– Vascular endothelium– Alveolar epithelium (type I pneumocyte)
• ARDS: Injury to, and compromise of, either barrier
– Increased vascular permeability• Alveolar flooding (exudative/protein‐rich)
– Hyaline membrane formation• Loss of diffusion capacity• Damage to type II pneumocytes widespread surfactant
abnormalities
20Source: Husain AN. The Lung. In: Kumar V, Abbas AK, Fausto N, Aster JC, eds. Robbins and Cotran Pathologic Basis of
Disease 8e. Philadelphia, PA: Saunders; 2010: 677‐737.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Imaging Choices in ARDS• Chest radiograph
– To support a diagnosis of ALI/ARDS in patients fulfilling clinical
criteria– To detect or confirm a suspected subclinical complication (e.g.,
nosocomial pneumonia)
– To monitor progression or regression of prior findings• CT
– To quantify the extent of lung abnormality in patients with
equivocal CXR
– To determine the etiology of the ARDS– To identify areas of dependent, dense, parenchymal
opacification (compression atelectasis)
21
Sources:Desai SR. Acute respiratory distress syndrome: imaging of the injured lung. Clin Radiol. 2002;57(1):8‐17.Desai SR, Wells AU, Suntharalingam G, Rubens MB, Evans TW, Hansell DM. Acute respiratory distress syndrome
caused by pulmonary and extrapulmonary injury: a comparative CT study. Radiology. 2001;218(3):689‐93.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Stages of ARDS
• ARDS is comprised of three stages, each of which demonstrates distinct radiographic
findings.1.
Exudative Stage
2.
Proliferative Stage
3.
Fibrotic Stage
22
Andrew Chalupka, MS IIIGillian Lieberman, MD
Stages of ARDS: Exudative Stage
• Pathophysiologic: – Interstitial edema, rapidly progressing to the
filling/flooding of alveolar spaces with an exudate– Hyaline membrane formation
• Radiologic (plain film):– First 24 hours: normal CXR– Early: interstitial edema (perihilar)– Later: alveolar consolidation (peripheral); air
bronchograms
23
Sources: Gluecker T, Capasso P, Schnyder P, Gudinchet F, Schaller MD, Revelly JP, Chiolero R, Vock P, Wicky S. Clinical and
radiologic features of pulmonary edema. Radiographics. 1999;19(6):1507‐31.Desai SR. Acute respiratory distress syndrome: imaging of the injured lung. Clin Radiol. 2002;57(1):8‐17.
24Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 1:Early
exudative stage
Chest radiograph
25Source: Beth Israel Deaconess
Medical Center PACS
Perihilar,
interstitial
opacities
Companion Patient 1:Early
exudative stage
Chest radiograph
26Source: Beth Israel Deaconess
Medical Center PACS
Index Patient:Later
exudative stage
Chest radiograph
27Source: Beth Israel Deaconess
Medical Center PACS
Index Patient:Later
exudative stage
Chest radiograph
Peripheral,
alveolar
consolidation
Andrew Chalupka, MS IIIGillian Lieberman, MD
Stages of ARDS: Exudative Stage
• CT findings: Gravitational gradient– Ventral‐dorsal
• Anterior: normal lung• Posterior: dense consolidation• In between: ground‐glass opacification
– Cephalocaudal• Increasing abnormal density caudally
• CT findings: Airway changes– Bronchial dilatation
28
Sources: Gluecker T, Capasso P, Schnyder P, Gudinchet F, Schaller MD, Revelly JP, Chiolero R, Vock P, Wicky S. Clinical and
radiologic features of pulmonary edema. Radiographics. 1999;19(6):1507‐31.Desai SR. Acute respiratory distress syndrome: imaging of the injured lung. Clin Radiol. 2002;57(1):8‐17.
29Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 1
30Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 1
Normal lung
31Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 1
Ground‐glass
opacities
32Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 1
Dense
consolidation
33Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 1
Normal lung
Ground‐glass
opacities
Dense
consolidation
34Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 1
35Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 2
36Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 2:Later exudative stage
CT, axialImage 3
37Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 1
38Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 1
Normal
lung
39Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 1
Ground‐glass
opacities
40Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 1
Dense
consolidation
41Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 1
Dense
consolidation
Ground‐glass
opacities
Normal
lung
42Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 1
43Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 2
44Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 3
45Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 4
46Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 5
47Source: Beth Israel Deaconess
Medical Center PACS
Companion Patient 3:Later exudative stage
CT, axialImage 6
Andrew Chalupka, MS IIIGillian Lieberman, MD
Stages of ARDS: Proliferative Phase
• Pathophysiologic:– Organization of fibrinous exudate– Regeneration of alveolar lining
• Radiologic:– Inhomogeneous areas of ground‐glass opacity
– Thickening of alveolar septae
48Source: Gluecker T, Capasso P, Schnyder P, Gudinchet F, Schaller
MD, Revelly JP, Chiolero R, Vock P, Wicky S. Clinical and
radiologic features of pulmonary edema. Radiographics. 1999;19(6):1507‐31.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Stages of ARDS: Fibrotic Stage
• Pathophysiologic: – Scarring/fibrosis– Formation of subpleural and intrapulmonary cysts
• Radiologic:– Distortion of interstitial and bronchovascular markings
– Cystic lesions– Complications of cysts or barotrauma:
• Aberrant air: pneumothorax, pneumatocele
49
Sources: Gluecker T, Capasso P, Schnyder P, Gudinchet F, Schaller MD, Revelly JP, Chiolero R, Vock P, Wicky S. Clinical and
radiologic features of pulmonary edema. Radiographics. 1999;19(6):1507‐31.Goodman LR. Congestive heart failure and adult respiratory distress syndrome. New insights using computed
tomography. Radiol Clin North Am. 1996 Jan;34(1):33‐46.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Implications of Imaging for Understanding ARDS
• CT allows quantitative analysis of volumes of gas and tissue• CT data of the whole lung have changed our understanding
of the pathophysiology of ARDS– Lung volume = tissue volume + gas volume– We now understand that there is a marked
reduction
in overall
lung volume
at the expense of the volume of the lower lobes
• Increase in tissue in upper lobes (edema, inflammation)• Loss of aeration of lower lobes (compression by heart, abdominal
contents)
• Old understanding of ARDS: overall volume of lung preserved
because gain of tissue was expected to exceed loss of gas
• New understanding of ARDS: reduction
in overall lung volume
because loss of gas is greater than gain of tissue
– Loss of aeration differs between patients50Source: Rouby JJ, Puybasset L, Nieszkowska A, Lu Q. Acute respiratory distress syndrome: lessons from computed
tomography of the whole lung. Crit Care Med. 2003;31(4 Suppl):S285‐95.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Lower‐lobe predominant pattern
• 40% of patients
• Loss of aeration:
– Mainly in lower lobes
– Minimal involvement of
upper lobes
• Mortality: 40%
51
CT scan from a 74‐year‐old patient with
ARDS caused by severe bronchopneumonia
•Upper lobes: some parts remain normally
aerated (black)•Lower lobes: either poorly aerated (gray) or
nonaerated (red).
Image: Rouby JJ, Puybasset L, Nieszkowska A, Lu Q. Acute respiratory
distress syndrome: lessons from computed tomography of the whole
lung. Crit Care Med. 2003;31(4 Suppl):S285‐95.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Lower‐lobe exclusive pattern
• One‐third of patients
• Loss of aeration:
– Exclusively in lower lobes
• Mortality: 40%
52
CT scan from 50‐yr‐old patient with ARDS
caused by aspiration pneumonia
•Upper lobes: normally aerated (black).•Lower lobes: either poorly aerated (gray) or
nonaerated (red).
Image: Rouby JJ, Puybasset L, Nieszkowska A, Lu Q. Acute respiratory
distress syndrome: lessons from computed tomography of the whole
lung. Crit Care Med. 2003;31(4 Suppl):S285‐95.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Diffuse pattern• 25% of patients
• Loss of aeration:
– Massive
– Equally‐distributed throughout lung
• Mortality: 70%
53
CT scan from in a 53‐year‐old patient with
ARDS caused by Pneumocystis
jirovecii
•Entire lung: nonaerated
(red) or poorly
aerated (gray).
Image: Rouby
JJ, Puybasset
L, Nieszkowska
A, Lu Q. Acute respiratory distress syndrome: lessons from computed tomography of
the whole lung. Crit
Care Med. 2003;31(4 Suppl):S285‐95.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Implications of Imaging for ARDS Management
• CT has led to safer and more‐effective management of ARDS
– Understanding that overall lung volume and cephalocaudal
lung dimensions are reduced at the
expense of the lower lobes• Prone and semi‐recumbent positioning of patients
– Assessment of alveolar recruitment and detection of lung overinflation
• Optimization of PEEP: maximizing recruitment while
limiting barotrauma
54Source: Rouby
JJ, Puybasset
L, Nieszkowska
A, Lu Q. Acute respiratory distress syndrome: lessons from computed
tomography of the whole lung. Crit
Care Med. 2003;31(4 Suppl):S285‐95.
Andrew Chalupka, MS IIIGillian Lieberman, MD
Summary• The different causes of airspace opacification
on plain film have distinctive
radiographic appearances.
• Pulmonary edema is one such cause. It is possible to deduce the
origin of
pulmonary edema (cardiac, fluid overload, or ARDS) based on the
radiographic features of a chest film.
• ARDS is a clinical syndrome of severe dyspnea
of rapid onset and
hypoxemia in the setting of diffuse pulmonary infiltrates.
• ARDS is caused by diffuse lung injury that leads to leakage of alveolar
capillaries, allowing flooding of alveolar spaces with an exudate.
• The menu of imaging for ARDS includes plain film and CT.• ARDS has three phases (exudative, proliferative, and fibrotic), each of
which has distinct radiographic features.
• CT has changed our understanding of the pathophysiology of ARDS.• CT has changed our approach to the management of ARDS.
55
Andrew Chalupka, MS IIIGillian Lieberman, MD
References• Desai SR. Acute respiratory distress syndrome: imaging of the injured lung. Clin
Radiol.
2002;57(1):8‐17.
• Desai SR, Wells AU, Suntharalingam
G, Rubens MB, Evans TW, Hansell
DM. Acute respiratory
distress syndrome caused by pulmonary and extrapulmonary
injury: a comparative CT study.
Radiology. 2001;218(3):689‐93.
• Gluecker
T, Capasso
P, Schnyder
P, Gudinchet
F, Schaller MD, Revelly
JP, Chiolero
R, Vock
P, Wicky
S. Clinical and radiologic features of pulmonary edema. Radiographics. 1999;19(6):1507‐31.
• Goodman LR. Congestive heart failure and adult respiratory distress syndrome. New insights using
computed tomography. Radiol
Clin
North Am. 1996 Jan;34(1):33‐46.• Husain AN. The Lung. In: Kumar V, Abbas
AK, Fausto
N, Aster JC, eds. Robbins and Cotran
Pathologic Basis of Disease 8e. Philadelphia, PA: Saunders; 2010: 677‐737.
• Ketai
LH, Godwin JD. A new view of pulmonary edema and acute respiratory distress syndrome. J
Thorac
Imaging. 1998;13(3):147‐71.• Levy BD, Shapiro SD. Acute Respiratory Distress Syndrome. In: Fauci
AS, Braunwald
E, Kasper DL,
Hauser SL, Longo DL, Jameson JL, Loscalzo
J, eds. Harrison's Principles of Internal Medicine
17e.
New York, NY: McGraw Hill; 2008: 1680‐1684.
• Rouby
JJ, Puybasset
L, Nieszkowska
A, Lu Q. Acute respiratory distress syndrome: lessons from
computed tomography of the whole lung. Crit
Care Med. 2003;31(4 Suppl):S285‐95.• Trotman‐Dickenson B. Radiography for the Critical Care Patient. In: McLoud
TC, Boiselle
PM, eds.
Thoracic Radiology: the Requisites. Philadelphia, PA: Mosby; 2010: 136‐159.
• Wheeler AP, Bernard GR. Acute lung injury and the acute respiratory distress syndrome: a clinical
review. Lancet. 2007;369(9572):1553‐64.
56
Andrew Chalupka, MS IIIGillian Lieberman, MD
Acknowledgements
• The following individuals provided invaluable assistance in acquiring and interpreting
images:– Javier Perez‐Rodriguez, M.D.– Alexander Bankier, M.D.– Diana Litmanovich, M.D.– Paul Sprin, M.D.
• Thanks also to Emily Hanson for her logistical assistance.
57
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