Medical device reliability program

Improved Efficiency
& Reliability for
Servers using
Immersion Cooling
Chet Haibel
©2011 ASQ & Presentation Haibel
Presented live on Apr 12th, 2011
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Medical Device
Reliability Program
Originally Presented April 12, 2011
Revised September 14, 2013
Chet Haibel

Chet Haibel ©2013 Haibel Consulting LLC 4
Agenda
• Some of the many process-controlling documents
• Simplest process per the QSRs, MDD, ISO 13485
• Gathering all the Requirements and Specifications
• Making Risk Management (ISO 14971) painless
• Using Risk Management to highlight issues
• The shortest path is to add a step to the process
• Overstress testing substitutes for quantity and time
• Good Reliability Procedures

Chet Haibel ©2013 Haibel Consulting LLC
Some Controlling Documents
FDA’s QSRs: Title 21 CFR Part 820, esp. 820.30
European Union’s MDD 93/42/EEC
ISO 13485:2008 Medical Devices – Quality Management
Systems – Requirements for Regulatory Purposes
ISO 14971:2007 Medical Devices – Application of Risk
Management to Medical Devices
IEC 62304:2006 Medical Device Software – Software
Life Cycle processes
IEC 62366:2007 Medical Devices – Application of
Usability Engineering to Medical Devices
These don’t tell you how to make your product reliable!
5

Simplest Medical Device Program
6
Validate: Designed the right product
Verify: Designed the product right
Product
Development /
Innovation
Design
Verification
Design
Inputs
Design
Outputs
User
Needs
Prototypes
Design
Transfer
Production
Initial Units
Design
Validation
Production
Units
Design and Development
Planning
Design
History File

Focus on Gathering Design Inputs
7
Last minute changes really hurt reliability, cost, and
schedule, so do an exceptional job of gathering all the
inputs at the very start of the development project
There are actually a lot of “customers” of
New Product Development to keep happy

Seven Sources of Critical Information
8
Specification
Development
System
Requirements
User
Human
Factors
External
Standards
Service
Internal
Standards
Safety
Functional
Requirements
Usability
Requirements
Risk Control
Requirements
Consistency
Requirements
Maintainability
Requirements
System
Requirements
Specification
Marketing
Competitive
Requirements
Regulatory
Requirements
Requirements need
to be developed into
specifications
Complete specifications
are verifiable, including
fraction conforming at
statistical confidence

Setting Specifications
Stress, Time, or Cycles
Customer
Application
Low Specification
(perhaps 1σ)
Product
Performance
Stress, Time, or Cycles
Test must show that
large fraction of
product meets
specification
To demonstrate that a large fraction of the product meets
specification requires large sample size, long test time, or
large number of cycles
Low Specification
(perhaps 1σ)

High Specification
(perhaps 3σ)
Test must only
show that product
typically meets
specification
High Specification
(perhaps 3σ)
Stress, Time, or CyclesStress, Time, or Cycles
To demonstrate that a specification is typically met
requires small sample size (three?), short test time,
or small number of cycles
Customer
Application
Product
Performance

Tough Specifications mean Faster, Cheaper, Better Testing!
Better because testing to tougher specifications produces
failures,
and failures are good!
Failures show how much Design Margin exists
Failures produce numbers (Variable data) which are much
better than pass / fail (Attribute data)
Failures can be analyzed,
which leads to root cause understanding,
which gives opportunities for improvement

ISO 14971 (Risk Management) Requires
Risk Management Plan, which has six requirements:
the scope of the planned risk management activities,
identifying and describing the medical device and the life-cycle
phases for which each element of the plan is applicable;
assignment of responsibilities and authorities;
requirements for review of risk management activities;
criteria for risk acceptability, based on the manufacturer’s
policy for determining acceptable risk, including criteria for
accepting risks when the probability of occurrence of harm
cannot be estimated;
verification activities; and
activities related to collection and review of relevant production
and post-production information.
12

ISO 14971 Requires (continued 1)
Risk Analysis (typically FTA or FMEA)
Identification of the device and accessories
Identification of the persons / organization who did the analysis
Date of analysis
Intended use / intended purpose of the medical device
Identification of reasonably foreseeable misuse
Identification of qualitative and quantitative characteristics
that could affect safety
Identification of known or foreseeable hazards
Estimation of the risks for each hazard
(combination of Probability and Severity of each Harm)
13

14
Risk Evaluation per criteria in Risk Management Plan
Probability of Harm
Annual Probability per Device Negligible Marginal Critical Catastrophic
Frequent
Probable
Occasional
Remote
Improbable
Incredible
Acceptable Acceptable Acceptable Tolerable
1 in 1,000,000
Acceptable Acceptable Acceptable Acceptable
Severity of Harm
Intolerable Intolerable Intolerable Intolerable
1 in 100
Tolerable Intolerable Intolerable Intolerable
1 in 1,000
Acceptable Tolerable Intolerable Intolerable
1 in 10,000
Acceptable Acceptable Tolerable Intolerable
1 in 100,000

15
Risk Control
Risk reduction using “option analysis,” an integrated approach
of prioritizing risk control measures among three broad
categories: inherent safety by design, protective measures,
and information for safety
Verification of implementation of risk control measures
Verification of effectiveness of risk control measures
Identification whether new hazards have been introduced by
risk control measures
Assurance that all identified hazards have been evaluated
Evaluation of overall residual risk acceptability

16
Risk Management Report, summarizes a review of the risk
management process:
Reviewed by persons with appropriate authority;
Ensures the Risk Management Plan has been appropriately
implemented;
Ensures that the overall residual risk is acceptable;
Ensures that appropriate methods are in place to obtain relevant
production and post-production information.
Risk Management File, containing all risk management
documents; which is reviewed whenever conditions change
and is kept current as new information becomes available.

Painless Risk Management
As soon as the product concept exists, identify the hazards,
their worst outcomes, and do Fault Tree Analysis (FTA)
with each of these outcomes as Top Event of a Fault Tree
17
Wrong
Infusion
Rate
Motor Failure
Example: IV Pump
How can we “architect” the
product so these single
failures do not lead to this
Top Event?
RAM Failure
Operator Error

18
Wrong
Infusion
Rate
Operator Error
RAM Failure
Motor Failure
Dose Rate Calculator requires
another offsetting input error
Another independent failure in
complementary (shadow) RAM
Precise interfering quadrature
signals like the shaft encoder’s
Painless Risk Management (continued 1)
Fault Tree
Synthesis
During Product
Architecture

Identify all hazards at the initial concept phase and “architect”
the product to eliminate all single failures that lead to high
Severity Harm (I call this Fault Tree Synthesis)
19
Single
Failures
No Single Failure Results
in the Wrong Infusion Rate!
Initial Fault Tree

As soon as the steps in using the product can be listed,
generate an Application FMEA that deals with user
misunderstandings, omissions, commissions, and any user
interface issues including potential misuse and abuse
The aFMEA assumes the product will be designed and
manufactured correctly and deals with the whole system
As soon as key components & parts have been conceived,
generate a Design FMEA which considers what happens if
the part fails to do all its functions correctly
The dFMEA assumes the product will be manufactured
correctly but considers misuse and abuse from aFMEA
20

21
As soon as the earliest sketch of the production flow can be
made, generate the Process FMEA which examines the
effects of errors, commissions, and omissions at each step
in the manufacturing process
The pFMEA assumes the product will be designed cor-
rectly but considers misuse and abuse from the aFMEA
As soon as the field replaceable units (FRUs) can be identi-
fied, list the steps in diagnosing, removing and replacing
FRU, and verifying the repair; generate the Service FMEA
considering errors, commissions, and omissions in repair
The srFMEA assumes the product will be designed and
manufactured correctly but considers misuse and abuse
from the aFMEA

Feasibility Design V and V Production
Hazard Identification and
Fault Tree Synthesis
Application FMEA
Design FMEA
Review and Updates to
Risk Management File
Complaints
Risk Management
Plan
Verify RCMs are
Implemented and
Effective
Process FMEA
Post-Production
Risk Management
Report
ServiceYields
Regulatory
Submittals
Product
Architecture
22
Risk Control Measures
Fault Tree Synthesis guides product architecture
FMEAs guide design of product and manufacturing process
Risk Control Measures are developed into specifications
Design Verification achieves required verification of RCMs

Why This Emphasis on Risk Management?
The harm outcomes with high severity indicate where
verification must be done with larger reliability (fraction
conforming) at good statistical confidence Example:
Also, harm outcomes which require low probability of
occurrence are where reliability effort must be focused
Think it through carefully, record it in the Risk
Management documents, then let them guide
product / process design and reliability effort
23
Severity of Potential Harm Negligible Marginal Critical Catastrophic
Reliability (Fraction Conforming) 0.80 0.90 0.95 0.99

Simplest Medical Device Program
24
Validate: Designed the right product
Verify: Designed the product right
Product
Development /
Innovation
Design
Verification
Design
Inputs
Design
Outputs
User
Needs
Prototypes
Design
Transfer
Production
Initial Units
Design
Validation
Production
Units
Where best should Reliability testing fit in?

Where best to integrate Reliability?
The regulations lead one to think the shortest path is to submit
prototypes directly to Verification Testing to qualify the design
Trying to find reliability issues during Verification is ineffective
because:
Large sample sizes are too expensive unless tooling is done
Changes after tooling are expensive and schedule-destructive
Customer
conditions
are too mild
Sample Size
is too small
Can’t see issues
that will be caused
by long-term
manufacturing
variation
25Chet Haibel ©2013 Haibel Consulting LLC

Long-term Process Dynamics
Guideline: over time, a process tends to shift by 1.5
LSL USL
Shift
Happens
Short-Term
Capability
Cpk
Long-Term
Performance
Ppk

Marginal Component’s Strength and Load
Torque, Voltage, Current, etc.
One can build quite a
few prototypes before
encountering the tails
of the strength
distribution
Customer
Conditions
But when many units are built and used by many different customers,
a number of components will fail under normal customer conditions
Long-term
Performance
Most of the components
have been applied with
excellent design margin
and can take much more
than worst case customer
conditions
Design
Margin
Long-term
PerformanceCustomer
Conditions

Trying to find reliability issues
during Verification is ineffective
WRONG !! RIGHT !! Insert Rapid Discovery Step
28
Where best to integrate Reliability?

0
0.2
0.4
0.6
0.8
1
1.2
0
0.2
0.4
0.6
0.8
1
1.2
Drive this overlap
area up
Increase the load until the
first few components fail
These are components with marginal applications:
design weaknesses
This will necessitate going beyond customer conditions
29
Rapid Issue Discovery
Wide-Ranging
and Increasing
Load

Rapid Issue Discovery
We are substituting overstress testing for
sample size and time
Big Issue: Are failures found relevant or foolish?
WRONG METHOD !! Judging by the stress level
which caused the failure to occur
RIGHT METHOD !! Perform Failure Analysis to
gain Root Cause Understanding, then decide
whether customers will see the failure mode
30

Discovery versus Verification
Do this first, fast, and often
Fly Through Verification
Result: Shorter Schedule and Product that Doesn’t Fail
31
Signed-Off
Protocol with
Criteria for Succes
Test to
Requirements
Represen-
tative
Samples
Goal
is to
Pass
Statistically
Significant
Quantity
Formal Report
Demonstrating
Criteria for
Success Are Met
Test Beyond
Requirements
Earliest
Prototypes
Force
Failures
Minimum
Quantity
Short Report:
What was Done,
Failures to be
Analyzed

Operating Time (t)
HazardRate-h(t)
Useful-Life
Failures
Early-Life
Failures
Wear-
Out
Failures
Life to the Beginning of Wear-Out
Random-in-Time Failures
Find by Cycle Testing
Solution in Product Design
or Preventive Maintenance
Find by HALT
Solution in Designing
Product with Margin
Find by HASS
Solution in Mfg. Processes or
Shipping, Handling, Storage
Summary of Failure Types, How Found, and How Solved

Accelerated (Wear-Out) Test
If possible, set up a repetitive “cycle test” which removes the
“dead time” between cycles. But brainstorm what artifact the
test may be adding and / or what the test may be concealing
Test until a minimum of five failures are produced [Haibel’s rule]
Use Weibull Analysis to fit a distribution to the failure data
If life is not sufficient, determine the reservoir of material and
the process consuming the reservoir. Increase the reservoir
of material and / or slow down the process consuming it
If necessary, replace the reservoir of material periodically
with a scheduled preventive maintenance program

Deductive Accelerated (Wear-Out) Test
• Run three unequally sized groups of components (1, 2, 4
quantity ratio) at three levels of stress acceleration
– Smallest quantity run at 10% below the “foolish” level
– Middle quantity 20% below the “foolish” level
• Analyze failures: using Physics of Failure and Weibull
Analysis, estimate the life vs. stress relationship and
whether the component is on track to qualifying
• Based on Project Time resources, establish the lowest
stress level for the largest quantity group
– As close to customer conditions as time permits
– Conservative enough to finish within allotted time
• Project life at customer conditions from all three groups

What Are Your Questions?
Chet@HaibelConsulting.com

Medical device reliability program

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