exploring the berlin definition of ards
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EXPLORING THE BERLINDEFINITION OF ARDS
Niall D. Ferguson, MD, FRCPC, MScInterim Director, Critical Care Medicine
University Health Network & Mount Sinai Hospital
Associate Professor of Medicine & Physiology
Interdepartmental Division of Critical Care MedicineUniversity of Toronto
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jamanetwork.comCopyright restrictions apply.
Available at www.jama.com
The ARDS Definition Task Force
Acute Respiratory Distress Syndrome:The Berlin Definition
Published online May 21, 2012
An initiative of
Endorsed by
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Why Do We Need anARDS Defintion AT ALL?
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Reliable and Valid Definitions are
ESSENTIAL to Conduct andInterpret Clinical Research
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Importance to Researchers
Enable epidemiological studies
Facilitate enrolment into clinical trials
Allow comparison between studies
Enhance linkages between clinical and basic science Phenotype Genotype relationship
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Importance to Clinicians
Ability to implement results of positive RCTs in clinical
practice
Lower Vt for ALI
May also be useful in prognostic discussions with
patients/families
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Importance to Administrators
Epidemiological studies need definitions
These in turn may be useful in planning resource allocation
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The American-European Consensus
Conference on ARDSBernard et al. AJRCCM1994; 149:818-24
American-European Consensus (AECC)
PaO2/FIO2 200 * &
Acute onset &
CXR with bilateral infiltrates &
PAWP 18
*Regardless of PEEP level
or no clinical evidence of left atrial hypertension
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Sensibility Concerns - AECC
No definition of acute
Risk factors not included
Inconsistency of PaO2/FIO2 ratio
Effect of PEEP Effect of FIO2
PCWP & ARDS can coexist
Interpretation of the CXR has poor reliability
Crit Care Med 2008; 36:2912-2921
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Effects of Airway Pressure
PAW = 22 PaO2/FIO2 = 80 PAW = 30 PaO2/FIO2 = 281
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AECC Sensibility Concerns
No definition of acute
Appropriate clinical setting not formally
included
Inconsistency of PaO2/FIO2 ratio
effect of PEEP
effect of FIO2
PCWP and ARDS can coexist CXR interpretation has poor reliability
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26
Median PAWP (mm Hg)
% of
patients
with PA
catheters
Data from Stewart et al. NEJM1998 338:335-61
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29% had PAOP > 18
97% of these had N or
elevated CI
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Interobserver variability in
applying a radiographic
definition of ARDSRubenfeld et al. Chest1999 116:1347-53
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Interobserver variability in applying a radiographic
definition of ARDSRubenfeldet al. Chest1999 116:1347-53
21 clinical researchers and opinion leaders
28 CXRs from hypoxemic ICU patients
= 0.55 ( 0.02) for inter-observer agreement
13/28 CXRs showed near perfect agreement
Interobserver variation in interpreting chest
radiographs for the diagnosis of ARDSMeade et al.AJRCCM 2000 161:85-90
Intensivists and radiologists reading 778 CXRs fromPLVS study
= 0.38 to 0.55 for inter-observer agreement = 0.72 to 0.88 for inter-observer agreement after training
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The importance of recognising ALI
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From Ware & Matthay NEJM 2000
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Importance of Specificity in RCTs
Other Diseases
Specific TestNon-Specific Test
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Process
Appointment of Chairs
Selection of Panelists
Presentations & consensus discussions
Sept 30 Oct 1 2011, Berlin, Germany
Empiric evaluation of draft definition
Focus on feasibility, reliability, validity
Consensus revisions
Society endorsements
Evaluation of Berlin Definition
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Conceptual Model of ARDS
Panelists agreed that ARDS is:
A type of acute, diffuse, inflammatory lung injury Leading to increased pulmonary vascular permeability, increased
lung weight, loss of aerated lung tissue
Clinical hallmarks are hypoxemia, bilateral opacities, shunt, dead
space, decreased compliance
Morphologically DAD
Evolutionary not Revolutionary change
Maintain links to AECC definiton
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Berlin Draft Definition
Acute Respiratory Distress SyndromeTiming Within 1 week of a known clinical insult or new/worsening respiratory symptoms
Origin of EdemaRespiratory failure not fully explained by cardiac failure or fluid overload;
Need objective assessment (e.g., echocardiography) to exclude hydrostatic edema if no risk factor present
Mild Moderate Severe
Oxygenation b200
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Novel patient-level meta-analysis of 7 cohorts:
4 Clinical and 3 Physiological
Physiological Cohort
269 Patients
Clinical Cohort
4188 Patients
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Demographics of ARDS Clinical Cohort
2 population based cohorts
1 clinical trials cohort
1 academic hospitals cohort
N=4188Sites 56-79Years enrolled 1996-2007
Age (mean) 54.5Gender (% male) 57%Primary Risk Factor
Pulmonary Sepsis 35%Other Sepsis 34%
Trauma 7%
Other/None 24%PaO2/FiO2ratio mean 150PaO2/FiO2< 200 76%CXR with > 3quadrants
73%
Mortality 34%
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Evaluation Process - Analytic Framework
Evaluate the value of proposed ancillary variablesin defining the Severe ARDS subgroup in thedraft definition
Determine the distribution of patientcharacteristics across definition severitycategories
Determine the predictive validity for mortality of
the final Berlin Definition Compare the final Berlin definition to the AECCdefinition
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Evaluation of SevereAncillary variables identify a smaller group of patients with similar mortality
Draft ARDSPaO2/FiO2 < 100 mmHg
PEEP > 10 cm H2O
3 or 4 quadrant opacities on CXR
Crs < 40 ml/cm H2O
VeCorr > 10 L/min
Final ARDSPaO2/FiO2 < 100 mmHg
PEEP > 5 cm H2O
Bilateral opacities on CXR
45% Mortality
Moderate
64%
Mild
22%
Severe
14%
Mild
22%
Moderate
50%
Severe
28%
Mortality
45%
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Berlin Definition of ARDS
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Distribution of patients across categories
of ARDS
ARDS3670
Mild
Moderate
Severe
27%
Mortality
45%
Mortality
22%
50%
28%
32%
Mortality
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Predictive validity of Berlin Definition - Clinical
0
10
20
30
40
50
Mild Moderate Severe0
10
20
30
Mild Moderate Severe
Mortality % Ventilator Free Daysmedian
0
5
10
15
20
25
30
Mild Moderate Severe
Ventilator days survivorsmedian
P
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Predictive validity of Berlin Definition - Physiologic
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Conclusions
First study to combine consenus and evaluation of a critical
illness syndrome definition in a single iterative process
Berlin Definition addresses some of the limitations of the
AECC Definition for ARDS Provides training set of CXRs and Clinical Vignettes
Without evaluation a more complex definition that identified a
smaller subset of Severe ARDS patients would have been
adopted
Future modifications to critical illness syndrome definitions
should be guided by a process that combines empiric
evaluation with expert consensus
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Berlin Definition Limitations and Future
Directions
Predictive validity only one criterion for revised definition
While PEEP, compliance, chest radiograph, and dead space do notadd to predictive validity of Severe ARDS definition, they are importantvariables for clinicians to measure and understand in ARDS
Many variables and measures of interest (EVLW, Biomarkers, CT) notincluded in definition primarily due to feasibility concerns and lack ofdata on validity
Mechanistic variables may be included for study specific researchquestions (recruitability, inflammatory markers)
Other aspects of validity and reliability not empirically measured Anticipate further work to evaluate and improve the Berlin Definition
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The ARDS Definition Task Force
ChairsMarco Ranieri
Gordon Rubenfeld
Taylor Thompson
Data or statistical supportEllen Caldwell
Andrew Bersten
Dale Needham
Antonio Pesenti
Additional attendees
Salvatore Maggiore
Agostino GemelliAnders Larsson
Karen Pickett
MembersMassimo Antonelli
Antonio Anzueto
Richard Beale
Laurent BrochardRoy Brower
Luigi Camporota
Andrs Esteban
Eddy Fan
Niall D Ferguson
Luciano Gattinoni
Andrew Rhodes
Arthur S. Slutsky
Jean-Louis Vincent
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n.ferguson@utoronto.ca
October 28-31, 2012Sheraton Centre Hotel, Toronto
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