Clinical Engineering
Engineers in the Modern Academic Medical Center
Design Disasters
Consequences of Blunders, Bad Luck, and Bias
Patrick Norris, Ph.D.
Assistant Professor of Surgery,
Biomedical Engineering
patrick.norris@vanderbilt.edu
Clinical Engineering
Why do hospitals need engineers?
• Definition
• Past, Present, Future
• Examples
– Facility Design
– Biomedical Devices
– Information and Technology Management
• Clinical Research, Quality Improvement
Biomedical Electronics
Definition
Clinical Technology Service
Biomedical Engineering
Definition
The American College of Clinical Engineering:
A professional who supports and
advances patient care by applying
engineering and management skills to
healthcare technology.
Definition:
Hospitals need engineers when technology requires:
• Special (non-trade/craft skills)
customization or maintenance
• Complex selection criteria
• Modification of existing facilities or
systems, or special design of new ones
• Design and analytic skills, professional
credentials, etc. differentiate engineers
from technicians, craftspeople, clerical,
administrators, etc…
Examples: Past
• Einthoven: EKG, early 1900’s
• Other examples:
– Day to day heat,
AC, water,
electricity, etc.
Examples: Present
• Infrastructure Design
– Typical: Water, Electrical, HVAC, Telecom
– Special: Medical Gas, Sample Handling
– Structural: Imaging Systems
• Biomedical Devices
– Selection, integration, tracking
– Maintenance is becoming a sophisticated
trade/craft skill
• Information
Future
• Information
– Medical Informatics
– 6 VUSE PhDs
• Integration
– People
– IT Systems
– Medical Devices
• Regulation
– Privacy, Safety,
Efficacy
• Across Multiple
Healthcare Systems
Grimes SL, IEEE Engineering in
Medicine and Biology Magazine,
March/April 2003 p.91-99
Clinical Research
• SIMON Project
– (Signal Interpretation and Monitoring)
– Ongoing since 1994
• Seeks to Advance:
– Medical Monitoring Technology
– Critical Care
– Scientific Knowledge
• Clinical Engineering Component
Trauma
•
•
•
•
5th Leading Cause of Death (1st Under 45)
8% of Medical Expenditures (rank: 3rd)
All Age and Socioeconomic Groups
VUMC
– Only Level 1 Facility, 65,000 Square Miles
– 3500 Annual Admissions
– 800 to Trauma ICU, ~10% Mortality
Patient Monitoring
• Cushing, early 1900’s:
– Importance of Monitoring and
Recording Vital Signs
• Technology Has Advanced
• Fundamentally, Clinical
Strategies Remain Unchanged
– Intermittent Recording
– Manual Interpretation
Tools for
Dense Physiologic
Data Management
Four Engineering Challenges
• Data Collection
– Interfaces to a Variety of Devices
– Remote Locations
• Storage
– Clinical Applications - Short-Term
– Research Applications - “Forever”
• Processing
– Time-Critical Tasks (Clinical Decision Support)
– Research Analysis
• Architecture
– Integration, Reliability, Scalability, Flexibility…
SIMON Data Capture
• Philips CareVue
– Routine, Automatic
Vital Signs Capture
– HR, ABP, PAP, CVP,
ICP, CPP, PAP, SaO2
– Episodic Waveform
Capture
• Edwards Vigilance
– CI, EDVI, temp, SvO2,
etc.
• Alaris IV Pump (near
future?)
SIMON Data Storage
• Relational Database
– Time Constraints w/ Limited Resources
– Adaptive Sampling, ~0.25-1Hz Storage
• 5500+ TICU Patients
– Reliably Identified, Linked to Outcomes
• 450,000+ Continuous Hours
• Grows by:
– 2 Million+ Data Points/Day
– ~70 Patients/Month
Daily Reports
Data Display
Alerts
• Effective Alerting
– Right Information
– Right Person
– Right Time
• Process
– Event
– Alert
– Notification
– Response
SIMON Architecture
• Modular, Simple Components
– Scalable
– Reliable
– Flexible
• Time-Constrained
SIMONT1
SIMONS1
Data
Collection
Modules (1
per device)
Data Collector
ODBC
System Mgr.
SQL 2k
Bed 1
Database Mgr.
Bed 2
Event Engine
SIMONW1
Bed 3
(Secure WWW Server)
trauma.mc.vanderbilt.edu
Alert Engine
Notify Engine
Digi
Driver
•
•
•
Simon
Packet
Format
Census Agent
Census Monitor
sFTP
Report Engine
sFTP
VUMC Census
Bed 14
VUMC StarPanel
Research Hypotheses
New measurements, available through techniques
of dense data capture and analysis, will:
• Identify failure of communication
pathways (uncoupling)
• Linking systems, organs, cells,
proteins, and genes
• Illuminate underlying control
mechanisms
• …especially in the critically ill
Short-Term HRV - Survival
Percent Time, entire stay
1.5
N = 825
1.0
0.5
0
0
0.5
1.0
1.5
2.0
2.5
3.0
5-minute HR Standard Deviation
3.5
Short-Term HRV - Death
Percent Time, entire stay
1.5
N = 98
1.0
0.5
0
0
0.5
1.0
1.5
2.0
2.5
5-minute HR Standard Deviation
3.0
3.5
Short-Term HRV - Combined
Percent Time, entire stay
1.5
N = 923
1.0
0.5
0
Time normalized
within outcome
group
0
0.5
1.0
1.5
2.0
2.5
3.0
5-minute HR Standard Deviation
3.5
Design Disasters
Consequences of Blunders,
Bad Luck & Bias
• What is a Design Failure?
• Why Do They Happen?
• Examples
– “Recipes for Design Disasters”
– Space Program
– Transportation
– Medical
What is a Design Failure?
• Elements of Establishing Defect:
– Identify the design defect
– Establish a causal link to harm or cost
– Identify alternate designs (correctable)
– Compare to similar products
• “A product does not have a design defect when it
is safe for any reasonably foreseeable use and
meets all applicable functional specifications.”
Geddes, Medical Device Accidents With Illustrative Cases
Example Design Defect
(probably from urban legend)
Nurses in Pelonomi Hospital, South African
hospital were baffled that every Friday morning
the patient in one particular bed would be found
dead! Investigation revealed that the cleaning
person would unplug that bed’s life support
equipment, in order to plug in her floor polisher
when she did the floors each Friday. When
finished, she would plug the equipment back in
unaware that the patient was now dead.
Example Design Defect
Definition
• Identify defect
• Causal link
• Alternate designs
• Comparison
Pelonomi Hospital Legend
• Life support equipment
could be unknowingly
unplugged
• Staff were not alerted
when machine
unplugged, patient died
• Alarms and batteries
• All life-critical
equipment offered by
vendors X,Y,Z have
alarm & battery backup
What is a Design Failure?
• There are plenty of definitions
• Numerous example cases
• In the end, failures are debatable
– Ultimately, court may have to decide
– With testimony from experts
– Sometimes difficult to separate liability
from design flaw
– Negligence is a legal, not technical,
term
Why Do Designs Fail?
At least three types of factors
• Blunders (Human Error)
– “Everyone makes mistakes”
• Bad Luck (Random Effects)
– “S*** happens”
• Bias
– People sometimes believe what they
want to, irrespective of facts
– Especially when money, power,
relationships are involved
Example: $125M Blunder
• 1999 Mars Orbiter
• JPL, Lockheed
• Metric vs. English
units
• Erroneous orbital
entry calculation –
engine burn time
Example: Bad Luck (?)
• Weather: A random effect
• Dense fog on I-75
– 99 vehicle pile-up in TN
– Killing 12, injuring 56
• Initially weather blamed
• Then local paper mill
– $13.5M settlement
– Once = bad luck
– Many times = negligence?
Example: Bad Luck
• Tacoma-Narrows bridge
• Unforeseeable consequence of
lightweight design, wind profile
• No human deaths
• $5.2M in 1940,
~$70M today
• (Insurance paid)
Types of Bias
• “Statistical”
– Sampling
– Multiple comparisons
– Repeated measurements
• Psycho-Social
– Groupthink
– “Corpthink”
Examples: Statistical Bias
• More people die in hospitals than
anywhere else, therefore don’t go to
the hospital! (unfair sampling)
• Similar situation: A medical device
designed only for the critically ill
• Randomized, controlled trials are
part of the answer
Examples: Statistical Bias
• Suppose you design a device that
will roll a six every time – how many
times do you need to test it?
• Which results do you report?
• Increasingly an issue in medical drug
and device trials
• 95% significance (p<.05) means that
1 in 20 studies is a false-positive
Psycho-Social Biases
• Individual
– Primacy: The first option mentioned
seems best
– Recency: The last option seems best
• Group
– Groupthink: Consensus rules
– “Corpthink”: Desire to please those
higher in the chain of command
NASA: Ripe for Disaster?
• Huge shift in corporate culture
– Space race: Do it at any cost
– Increasing cost concerns, cuts,
downsizing, resource pressure, etc.
• Feynman, Challenger Disaster Report
– Engineer estimate of catastrophic
failure: 1 in 100
– Management: 1 in 100,000
– “What is the cause of management’s
fantastic faith in the machinery?”
More Design Failures
• “Recipes for Disaster”
– Ignition Source + Flammable Material
–…
• More Examples
– Transportation
– Space Program
– Software
Hindenburg
• German airship
• Caught fire while
landing in 1937
• Design defect:
– Hydrogen?
– Skin?
http://www.youtube.com/watch?v=F54rqDh2mWA
Apollo 1
• Pad fire during test
• Killed 3 astronauts
• Design defects:
– 31 miles of electrical wire
– Pressurized pure oxygen
environment
– Flammable materials
– Substandard wiring
Medical Devices & Fire
Ignition Source
• Electrocautery
• Nerve stimulators
• Short-circuit
• Electrostatic discharge
• Cigarettes
• …
Flammable Materials
• Anesthetic gas
– not so much today, ex. O2
• Gases in the body,
especially GI system
– Geddes reports ~10 cases
of GI explosions during
procedures, some lethal!
• Bedding, clothing
• Bandages
• Cleaning solutions,
solvents, etc.
Medical Software Design
• What type of [medical] technology is
least regulated?
– Software
– There is no professional-level (i.e. PE)
certification for software engineering
– Less regulation than devices/drugs
Medical Software Design
• Design failures are being publicized
• Computerized Physician Order Entry
– Cedars-Sinai software rollout
– Multi-million dollar project scrapped
– Software “endangered patient safety”
– This story is not unique
• Privacy issues
• Will software design failures increase?
Summary – Clinical
Engineering
• Definition of clinical engineering
• Engineers’ role in the hospital?
– Technology design, management
– Increasingly, information management
– Clinical research, i.e. VUMC Trauma
• Differences between engineering and
trade/craft skills (design & analysis)
Summary – Design
Disasters
• Geddes definition of design failure:
– Identified defect
– Causal link to harm
– Available alternative
– Deficiency w/ respect to other products
• 3 factors in design disasters:
– Human error (blunder)
– Random effects (bad luck)
– Bias
Sample Questions
Which is not an aspect of
establishing design failure
(according to Geddes)?
What factor best
differentiates engineers
from trades/craftspeople?
A.
B.
C.
D.
A. Design and analytic
skillset
B. Professional ethics
C. Ability to work in
highly regulated fields
D. Salary
Identified defect
Causal link to harm
Negligence
Feasible alternative
design
Sample Questions
What kinds of bias is most
likely encountered by an
individual doing statistical
analysis of complex data?
A.
B.
C.
D.
Unfair sampling
Groupthink
Recency
All of the above
According to Feynman’s
appendix to the
Challenger disaster
report, NASA engineers
estimate probability of
failure at about 1 in
________, compared to
management’s 1 in
________ .
A. 10, 10000
B. 1000, 1000
C. 100, 100000
D. 10000, 100
References/Sources
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clinicalengineering.duhs.duke.edu/
cms.clevelandclinic.org/anesthesia/body.cfm?id=124
www.healthsystem.virginia.edu/internet/clinical-eng/
www.wikipedia.org
www.ceasa-national.org.za/
www.mc.uky.edu/clinicalengineering/
cms.clevelandclinic.org/anesthesia/body.cfm?id=156
www.uams.edu/ClinEng/default.aspx
simon.project.vanderbilt.edu/
tafkac.org/medical/hospital_cleaning_lady.html
www.cnn.com/TECH/space/9909/30/mars.metric.02/
mars.jpl.nasa.gov/msp98/orbiter/
www.douglasjfeeslaw.com/achievements.jsp
gtresearchnews.gatech.edu/reshor/rh-ss01/fog.html
www.ralentz.com/old/space/feynman-report.html
youtube.com
patrick.norris@vanderbilt.edu