8/16/2011
Outline
• Human Factors Engineering
Taxonomy for Causal Analysis
• Survey of Existing Causal Taxonomies
• The WGPE Causal Taxonomy
Steven Sutlief, PhD
AAPM Working Group for Prevention of Errors
August 3rd, 2011
Books - General
Human Error
Jim Reason - 1990
Normal Accidents
Charles Perrow - 1984
• Validation Exercise
Books – Institutes of Medicine
To Err is Human
1999
Crossing the
Quality Chasm
Patient Safety
2003
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Reason’s Swiss Cheese Model
Holes
Theoretical Framework for
Error Classification Schemes
Active
Failures
Layers
Defenses
Barriers
Safeguards
Latent Conditions
Error-provoking
Long lasting holes
conditions within the or weaknesses in
local workspace
the defenses
Slips
Time pressure
Untrustworthy
alarms
Lapses
Understaffing
Untrustworthy
indicators
Fumbles
Inadequate
equipment
Unworkable
procedures
Mistakes
Fatigue
Design deficiencies
Procedural
variations
Inexperience
Construction
deficiencies
Reason’s Classification
of Errors
Not an error:
no prior intention to act
Error:
prior intention to act
Involuntary or
non-intentional
action
Spontaneous
or subsidiary
action
Slips/Lapses: failure of
actions to go as
intended
Mistakes: failure of intended
actions to achieve their desired
consequences
E.g., someone
stung by a bee
drops a plate she
is holding
Well-practiced
actions
sequences
pushed to the
subconscious
level.
Slips:
potentially
observable
Soundness
shortcomings –
sufficient
contingencies,
soundness of
judgment, etc.
Lapses:
more
covert
error
forms
Execution
Shortcomings
–failure to
achieve stated
objectives
Mistakes
Slips
Lapses
E.g., although one intentionally decides to drive
to work, many steps, such as opening the car
door, occur with little attentive consideration.
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Reason’s Error Types
and Error Forms
Error Type:
Cognitive stage:
Error Form (e.g.):
Relates to the origin of the
error within the sequence
of conceiving and
executing the action
The three broad stages in
the sequence of conceiving
and executing the action
Recurrent varieties of
fallibility… rooted in
universal cognitive
processes.
Mistakes
Planning
Lapses
Storage
Slips
}
Execution
Similarity,
Frequency Biases
Jen Rassmussen’s
Three Performance Levels
{
Knowledge-based level
Rule-based level
Skill-based level
Reason’s Classification
of Taxonomies
Behavioral Level
Based on more
immediate
consequences
(e.g.):
• Damage (nature
and extent)
• Injury (nature
and extent)
Based on formal
characteristics (e.g.):
• Omission-commission
• Repetition
• Mis-ordering
• Recoverability
• Human-vs-machine
• Operator-vs-design
“The evidence indicates
• that members of the same behavioral error
class can arise from quite different causal
mechanisms and
• That members of different behavioral
categories can share common aetiologies.”
Contextual Level
Conceptual Level
Acknowledge critical
relationship between
error type and the
situation in which is
appears. May
reference contextual
triggers such as
anticipations or
perseverations.
Seek to identify
underlying causal
mechanisms.
“Can’t explain why
the same…
circumstances don’t
always trigger the
same errors.”
“Based more upon…
theoretical inferences
than on observable
characteristic of the
error.”
Uses assumptions
about cognitive
mechanisms at work.
Causal Taxonomies – General
Comparison of Taxonomies
• ACCERS: Aviation Industry
• STAMP: General (Nancy Leveson)
• HEPS: Nuclear Power Industry
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Causal Taxonomies – General
STAMP
HEPS
Policies or
Procedures (7)
ACCERS
Inadequate Enforcement of
Constraints (Control Actions) (8)
Oral Communication (5)
Human Error (8)
Inadequate Execution of Control
Action (3)
Written Procedures (9)
Human Factors (21)
Inadequate or missing feedback
(4)
Workplace design/
physical environment (8)
Organizational
Factors (11)
Working environment (4)
Hardware (7)
Task supervision (4)
Weather or
Environment (11)
Training (4)
Airspace or ATC (11)
76 nodes
15 nodes
Eindhoven
University
The Joint
Commission
World Health
Organization
TERCAP
Organizational
(5)
Systems –
Organizational (7)
Organizational/
Service (4)
Attentiveness/ Surveillance
(2)
Technical (4)
Systems –
Technical (4)
Work/
Environment (4)
Intervention (4)
Human (11)
Intentional human
behavior (6)
Staff factors (35)
Prevention (3)
Patient factors (35)
Other factors
(2)
Unclassified (3)
External Factors
(3)
Clinical Reasoning (5)
Interpretation of provider’s
orders (6)
Professional responsibility/
patient advocacy (9)
20 nodes
81 nodes
• Eindhoven University: PRISMA-Medical: A
Brief Description.
• The Joint Commission: The JCAHO patient
safety event taxonomy
• World Health Organization : Towards an
International Classification for Patient Safety
• TERCAP: from the National Council of State
Boards of Nursing.
34 nodes
Causal Taxonomies – Medicine
22 nodes
Causal Taxonomies – Medicine
29 nodes
Causal Taxonomies – Rad. Onc.
• HTA: A Reference Guide for Learning from
Incidents in Radiation Treatment. Alberta
Heritage Foundation for Medical
Research, Health Technology Assessment.
2006.
• Madison: The Madison Medical
Taxonomy, described in Taxonomic Guidance
for Remedial Actions [Thomadsen 2005] .
• ROSIS/SAFRON: IAEA Voluntary reporting.
• WGPE: AAPM Working Group for Prevention
of Errors (this work).
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Causal Taxonomies – Rad. Onc.
HTA Canada
Madison
SAFRON (=HTA)
AAPM WGPE
Job factors (18)
Human Error (11) Job factors (18)
Organizational
Management (39)
Systemic/
Management (15)
Organizational
Shaping Factors
(19)
Systemic/
Technical (21)
Management Factors
(15)
Personal Factors
(10)
External (6)
Personal Factors (9)
Major Categories in the AAPM
WGPE Causal Taxonomy
Human behavior –
Staff (6)
Human Behavior –
Patient (5)
Natural Factors
(6)
Natural Factors (5)
External Factors (2)
Procedural Issues
(23)
49 nodes
36 nodes
47 nodes
96 nodes
WPGE Causal Taxonomy 1:
Organizational Management
a. Planning for program maintenance or
expansion (11)
b. Policies, Procedures, Regulations (6)
c. Training; acquiring and transmitting
knowledge and skills (4)
d. Communication (7)
e. Physical Environment (3)
f. Leadership and external issues (8)
Total number of nodes: 39
WPGE Causal Taxonomy 2:
Technical
a. Proper acceptance testing and commissioning
of new equipment (4)
b. Equipment design and construction issues (7)
c. Equipment maintenance issues (5)
d. Environment (within the facility) (5)
Total number of nodes: 21
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WPGE Causal Taxonomy 3-5
3. Staff-focused human behavior (6)
4. Patient-focused circumstances (5)
5. External Factors (beyond Facility Control) (2)
WPGE Causal Taxonomy 6:
Procedural
a. Failure to detect a developing problem (4)
b. Failure to interpret the nature of the
developing problem (4)
c. Failure to select the correct rule to address
problem (6)
d. Failure to develop an effective plan (4)
e. Failure to execute the planned action (5)
Total number of nodes: 23 (Grand Total: 96)
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Validation Sources
Validation
Number of Reported Causes
Falling in Each Category
WGPE Taxonomy
Categories
Number of
Reported Causes
Organizational
Management (39)
25
Technical (21)
15
Human behavior –
Staff (6)
27
Human Behavior –
Patient (5)
0
External Factors (2)
0
Procedural Issues
(23)
NA
Total
72
•
•
•
•
•
•
•
Epinal, France incident in 2006
Glasgow, Scotland SRS incident in 2006
WHO Toft Report on Radiotherapy Incidents
New York MLC incident in 2005
Ottawa, Canada Orthovoltage incident
IAEA: Bialystok, Panama, Costa Rica
ROSIS event database
Conclusions
• Through a consensus-building process, a casual
taxonomy has been created based on the
collective experience of the WGPE workshop
participants.
• Although the taxonomy is large relative to other
published taxonomies, it has been compressed to
three levels in order to make it more easily
navigable in an electronic implementation.
• The WGPE taxonomy attempts to include
conceptual causes as well as contextual and
behavioral causes.
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