Medical Device Maintenance and Sources of Obtaining Medical Device- Related Failure Data

1
Medical Device Maintenance and Sources of
Obtaining Medical Device- Related Failure Data

• Chapter 6
• Howell, Murray, Pierre

2
Introduction

• Maintenance is an important element of the
  engineering equipment life cycle.
• Failure data are the backbone of medical-related
  reliability studies.
• Provides invaluable information to professional
  involved with the design, manufacture and
  maintenance of future medical devices/equipment.
• This chapter presents various important aspects
  of medical device maintenance and sources for
  obtaining medical device-related failure data.

3
Medical Equipment Classifications

• Imaging and radiation therapy
• Life Support and therapeutic
• Patient diagnostics
• Patient environmental, transport
• Laboratory apparatus
• Miscellaneous

4
Medical Equipment Maintenance Indexes

• Used to measure different aspects of the
  maintenance function
• Indexes (6)
• Broad Indexes (3)
• Health-Care-Specific Indexes (3)

5
Index I
Relates the total maintenance cost to the total
investment in plant and equipment

• where
• IX1 index parameter
• Cm total maintenance cost
• TI total investment in plant and equipment

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Index II
Deals with total sale revenue

• where
• IX2 index parameter
• Cm total maintenance cost
• TSR total sale revenue
• Generally, average expenditure for the
  maintenance activity for all industry is around
  5 of the sale revenue.

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Index III
Relates the total maintenance cost to the total
output by the organization

• where
• IX3 index parameter
• Cm total maintenance cost
• TOT total output expressed in tons, megawatts,
  gallons, etc.

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Index IV
Provides number of repair requests accomplished
per medical device

• where
• IX4 index parameter or the number of repair
  requests accomplished per medical
  device/equipment
• a total number of medical devices
• TNRR total number of repair requests

9
Index V
Measures how much time elapses from a customer
request until the malfunctioning medical
device/equipment is repaired and put back into
full service

• where
• IX5 index parameter or the average turnaround
  time per repair
• ? number of work orders or repairs
• TATa total turnaround time

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Index VI
Defined by

• where
• IX6 index parameter
• Cp procurement cost or the cost at the time of
  purchase of equipment
• Cs service cost or the total of all parts,
  materials, and labor costs for scheduled and
  unscheduled service also includes in-house,
  vendor, prepaid contracts, and maintenance
  insurance expenses.

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Index VI (Contd)
Defined by

• Advantages
• Easy to compare across equipment types
• Takes into consideration all types of service
  costs
• Can be used with incomplete data
• Disadvantages
• Allows no compensation for the age of the
  equipment
• Requires a standard definition for the pricing of
  in-house service
• Possesses no mechanism for adjusting wage rates
  by geographic region

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Medical Equipment Computerized Maintenance
Management Systems (CMMS)

• Used by hospital clinical engineering departments
  for
• Collecting
• Storing
• Analyzing
• Reporting
• data on the repair and maintenance performed on
  medical devices/equipment.
• These data are used in areas such as
• Equipment Management
• Work Order Control
• Quality Improvement Activities
• Reliability and Maintainability Studies
• Cost Control

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Computerized Maintenance Management Systems (CMMS)
1. Define the problem scope

• Major steps in selecting a commercial CMMS
• Defining the problem scope for clinical
  engineering department
• Evaluating the effectiveness of the existing
  system
• Evaluating the commercially available CMMS
• Evaluating the chosen one or more CMMS with
  respects to identified requirements.
• Having discussions on potential performance
  issues with organizations of similar size and
  scope
• Evaluating the vendor support services
• Developing preliminary budget and cost estimates

2. Evaluate the current system in use
3. Conduct a preliminary study of all
commercially available systems
4. Conduct a comprehensive study of the selected
CMMS
5. Discuss all potential performance issues
concerning the above chosen CMMS
6. Carefully examine all CMMS support issues
7. Examine CMMS cost
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Mathematical Models for Medical Equipment
Maintenance

• Model 1
• Used to determine optimum time between
  item/equipment replacements.
• Average annual cost composed of avg. maintenance
  costs, avg. operating cost and avg. investment
  cost.
• Minimizes the equipment/item average cost with
  respects to its life.

• EAAC EOCf EMCf EIC (t-1)

(i j)
t 2
Where EOC is the equip/item operating cost for
the 1st year EMC is the equip/item maintenance
cost for the 1st year EIC is the equip/item
investment cost t is the equip/item life
expressed in years j is the amount by which
maintenance cost increases annually i is the
amount by which operating costs increases annually
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Model 1 continued

• By differentiating the equation with respects to
  t ten equating it to zero we obtain the following
  expression
• t ( )
• Where
• t is the equipment/item optimum-replacement
  interval

• Example assume the following
• j 500
• i 4,000
• EIC 50,000
• t ( )
• 4.71 years

1/2
2(50,000) 4000 500
1/2
2EIC i j
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Model 2

• Used to predict the number of spares required for
  a medical equipment/device in use
• T ?t z ?t ½
• Where
• T is the number of spares
• t is the mission time
• ? is the constant failure rate of the medical
  item under construction
• Z is associated with the cumulative normal
  distribution function.

• Example assume that the constant failure rate of
  a medical device is 0.0005 failures per hour.
  Determine the number of spare medical devices
  required during a 5,000-hour time period, if the
  confidence level for o stock out of the devices
  is 0.9032.
• From table z 1.3
• T (0.0005)(5,000) (1.3) (0.0005)(5,000) ½
• 5 medical devices are needed

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Medical Device-Related Failure Data Sources

• These are some sources for obtaining medical
  device-related failure data

Universal Medical Device Registration and
Regulatory Management System (UMDRMS)
Hospital Equipment Control System (HECS)
Sources
Medical Device Reporting System (MDRS)
MIL-HDBK-217
NUREG/CR-1278
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Hospital Equipment Control System (HECMS)

• Provides effective support and analysis of
  clinical engineering-related operations through
  detailed work scheduling of items.
• Provides objective and good quality data on the
  basis of satisfactory statistical foundation.
• Provides cost-effective, economic, financial,
  productivity data within the framework of each
  hospital.
• Provides new information support, including data
  on the relative reliability of competing brands
  and models of clinical equipment.

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(MDRS)

• The Medical Device Reporting System
• It is managed by the Center for Devices and
  Radiological Health, Food and Drug Administration
  (FDA).
• It contains reports filed by device manufacturers
  concerning patient deaths and serious injuries
  allegedly involving their manufactured items, as
  well as failure of such items that may have
  caused serious injuries or deaths.

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(UMDRMS)

• The University Medical Device Registration and
  Regulatory Management System
• It was developed by ECRI (Emergency Care Research
  Institute) and is designed to facilitate items
  such as tracking products for recall, safety, and
  reliability statistics and inventory control.

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MIL-HDBK-217

• It was developed by the U.S Department of
  Defense
• It is widely used in the industrial sector to
  predict the failure rate of a given piece of
  equipment.
• It contains generic failure rates for various
  parts, particularly the electronic ones, and a
  large number of mathematical models to predict
  failure rates of various types of parts in their
  actual use environment.
• This document can also be used to predict failure
  rates of medical equipment/devices or their parts.

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NUREG/CR-1278

• It was developed by the U.S. Nuclear Regulatory
  Commission to perform human reliability analysis
  with emphasis on nuclear power plant
  applications.
• The document contains failure data on various
  types of tasks performed by humans.
• The information contained in the document could
  be quite useful analyzing medical devices in
  regard to the occurrence of human error.

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Organizations for Obtaining Medical
Device-Related Failure Data

• There are many organizations that can be quite
  useful, directly or indirectly, in obtaining
  medical device-related failure data
• Center for Devices and Radiological Health, Food
  and Drug Administration, 1390 Piccard Drive,
  Rockville, Maryland 20857
• Emergency Care Research Institute (ECRI), 5200
  Butler Parkway, Plymouth Meeting, Pennsylvania
  19462
• Parts Reliability Information Center (PRINCE),
  George C. Marshall Space Flight Center,
  Huntsville, Alabama 35812
• Reliability Analysis Center, Griffiss AFB, U.S
  Department of commerce, 5285 Port Royal,
  Springfield, Virginia 22161

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Medical Device Failure-Related Data

• A wide variety of failure-related data, directly
  or indirectly, concerned with medical
  equipment/devices is available in the published
  literature.
• There are two types, directly or indirectly, of
  failure-related data
• Medical device specific data are concerned with
  the preproduction cause of a total of 1, 143
  medical device recalls for the period 1983 to
  1987. The causes of these recalls were grouped
  under 7 distinct categories device and
  process(design and software), component, label,
  and package (design).
• The general component-related failure data.