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									               MEDICAL DEVICES AND SOFTWARE




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 Medtronic ICD software upgrade targets Sprint Fidelis
 lead-fracture issue
 September 5, 2008
 Steve Stiles, Rockville, MD

 The US FDA has approved a software upgrade from
 Medtronic designed to warn patients of a possible
 fracture in Sprint Fidelis leads connected to its
 implantable devices with defibrillator capability. Most
 of the patients with the Sprint Fidelis lead still have the
 device implanted because of the surgical risk
 associated with removal.

 Devices with the new feature, the Lead Integrity Alert
 (LIA), will sound a warning when it detects signals that
 could be associated with lead fracture and repeat it
 every four hours until the patient's physician
 addresses the problem,


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               MEDICAL DEVICES AND SOFTWARE


A medical device is defined as “any instrument, apparatus,
appliance, material or other article (whether used alone or in
combination, and including the software necessary for its proper
application)” intended by the person under whose name it is to be
supplied, to be used for human beings for the purposes of one or
more of the following:
•diagnosis, prevention, monitoring, treatment or alleviation of
disease,
•diagnosis, monitoring, treatment, alleviation of or compensation for
an injury or handicap,
•investigation, replacement or modification of the anatomy or of a
physiological process,
•control of conception,

and does not achieve its principal intended action in or on the
human body by means, but which may be assisted in its function by
pharmacological, immunological or metabolic such means or any
required accessory to such an instrument, apparatus, appliance,
material or other article.

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                    FDA: SOFTWARE DEVICES



     Medical devices that contain one or more software
     components, parts, or accessories, or are composed solely of
     software are known as “software devices.”

     Software devices include:
     •firmware [small, fixed software programs] and other means
     for software-based control of medical devices
     •stand-alone software applications
     •software intended for installation in general-purpose
     computers
     •dedicated hardware/software medical devices.
     •accessories to medical devices when those accessories
     contain or are composed of software.




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       FDA GUIDELINES FOR SOFTWARE DEVELOPERS


   Inadequate or inappropriate software development life cycle
   and risk management activities, inappropriate use of a
   Software Device, or operational errors can result in a variety of
   potential failures or design flaws. Examples include:

   •unsafe or ineffective delivery of energy, drugs [e.g. pump
   operates continuously]
   •failure of life-supporting or life-sustaining functions [e.g.
   defibrillator voltage too low]
   •delivery of incorrect or incomplete information causing a
   misdiagnosis [e.g. density of bone in osteoporosis]
   •selection of the wrong treatment or therapy [e.g. defibrillator
   provides continuous shocks]




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             SOFTWARE DEVICES: LEVELS OF CONCERN



          “Level of Concern” is an estimate of the severity of
          injury that a device could cause, directly or indirectly, on
          a patient or operator as a result of
          •device failures
          •design flaws
          •routine operation [for its intended use].

          LEVELS OF CONCERN
          •Major
          •Moderate
          •Minor




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             SOFTWARE DEVICES: LEVELS OF CONCERN


 • Major level of concern
   A failure or latent flaw could directly or indirectly result in
   death or serious injury to the patient or operator through
   incorrect or delayed information or through the action of a
   care provider.

 2. Moderate level of concern
 A failure or latent flaw could directly or indirectly result in minor
    injury to the patient or operator through incorrect or delayed
    information or through the action of a care provider.

 3. Minor level of concern
    Failures or latent design flaws are unlikely to cause any
    injury to the patient or operator.




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                      SOFTWARE DOCUMENTATION

   SOFTWARE                                          MODERATE                MAJOR
                           MINOR CONCERN
   DOCUMENTATION                                     CONCERN                 CONCERN
                           A statement indicating the Level of Concern and a description of
   Level of Concern
                           the rationale for that level.
                           A summary overview of the features and software operating
   Software Description
                           environment.
   Device Hazard           Tabular description of identified hardware and software hazards,
   Analysis                including severity assessment and mitigations.
   Software                Summary of functional
   Requirements            requirements from         The complete SRS document.
   Specification (SRS)     SRS.
                           No documentation is       Detailed depiction of functional units and
   Architecture Design
                           necessary in the          software modules. May include state
   Chart
                           submission.               diagrams as well as flow charts.
                           No documentation is
   Software Design
                           necessary in the          Software design specification document.
   Specification (SDS)
                           submission.
                           Traceability among requirements, specifications, identified hazards
   Traceability Analysis
                           and mitigations, and Verification and Validation testing.
                                                     List of remaining software anomalies,
                           No documentation is
   Unresolved Anomalies                              explaining impact on safety or
                           necessary in the
   (Bugs or Defects)                                 effectiveness, including operator usage
                           submission.
                                                     and human factors.

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                SOFTWARE LIFE CYCLE ACTIVITIES



            •       Quality Planning
            •       System Requirements Definition
            •       Software Requirements Specification
            •       Software Design Specification
            •       Construction or Coding
            •       Testing
            •       Installation
            •       Operation and Support
            •       Maintenance
            •       Retirement



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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance
                          • Documentation of user needs
   •     Retirement       • Define tasks for each life cycle activity
                            •    Quality factors
                            •    Methods & procedure for each task
                            •    Inputs & outputs for each task
                            •    Risks & assumptions




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             SOFTWARE HAS ITS OWN LIFE CYCLE
                 WITHIN A MEDICAL DEVICE




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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance
                          • Identification, analysis & documentation of
   •     Retirement         intended use
                           •    Hardware/software operating conditions
                           •    User characteristics
                           •    User interactions/tasks
                           •    Potential hazards




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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance
                          • All software inputs & outputs
   •     Retirement       • All function the software will perform
                           • Definition of all user interfaces
                           • How users will interact with the system
                           • Errors and how they will be handled




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                    KEY SOFTWARE DOCUMENTS


    Software Requirements Specification [SRS]
    Includes functional, performance, interface, design,
    developmental, and other requirements for the software.

    Typical requirements that would be included in a SRS are
    •Hardware requirements [microprocessors, memory, sensors]
    •Programming Language Requirements
    •Interface Requirements [monitors, keyboard, etc.]
    •Software Performance and Functional Requirements [internal
    tests and checks, error handling, fault detection]
    •Stated or implied needs of customers and an organization's
    requirements

    The SRS describes what the software needs to do.




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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance
   •     Retirement
                      • Systems documentation
                      • Hardware required
                      • Parameters to be measured, recorded and/or
                        stored
                      • Data structures and data flow diagrams
                      • Error, alarm and warning messages
                      • Supporting software
                      • Risk analysis
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                    KEY SOFTWARE DOCUMENT


     Software Design Specifications [SDS]

     Describes how the requirements are implemented for
     the software device.

     This includes:
     • Software architecture and interrelationships
     • Software ‘module’ integration
     • Specifications for each module
     • Written documents, drawings, etc.
     • Verification and Validation protocols

     The SDS describes how the software will meet the
       design requirements described in the SRS.




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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance      • Programming language
   •     Retirement       • Use of libraries
                         • Error checking and debugging
                         • Traceability analysis
                         • Tests for modules and functions




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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance
                          • Test plan
   •     Retirement       • Methods
                         • Inputs, procedures, outputs & expected
                           results
                         • Documentation & reporting




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        SOFTWARE LIFE CYCLE ACTIVITIES: TESTING


        SRS specification
        [a] Data on 1000 patients must be stored
        [b] Visual alarm must sound when capacity
            reaches 950 patients

        Test Plan
        1. Load database with 948 patients.
        2. Add data for 2 patients.
        3. Confirm visual alarm is activated.

        NOTE: This is Design V……….




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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance
   •     Retirement
                    User site
                    • Pre-defined written plan
                    • Test procedures
                    • Test input data
                    • Evaluation of user interactions
                    • Acceptance criteria


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               SOFTWARE LIFE CYCLE ACTIVITIES


   •     Quality Planning
   •     System Requirements Definition
   •     Software Requirements Specification
   •     Software Design Specification
   •     Construction or Coding
   •     Testing
   •     Installation
   •     Operation and Support
   •     Maintenance
   •     Retirement

                     • Corrective maintenance [bug fixes]
                     • Perfective maintenance [improve performance]
                     • Plan for obsolescence




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                    The GHTF is still working on
                           software…


 New revision to EU medical device directives recognizes the need
 for special attention to software.

 “Taking account of the growing importance of software in the
 field of medical devices, be it as stand alone or as software
 incorporated in a device, validation of software in accordance
 with the state of the art should be an essential
 requirement.”

 “For devices which incorporate software or which are medical
 software in themselves, the software must be validated according
 to the state of the art taking into account the principles of
 development lifecycle, risk management, validation and
 verification.”

 October 2007

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                    The GHTF is still working on
                           software…




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                    SOFTWARE IS DIFFERENT


   • Problems are traceable to errors made during the design and
     development process.

   • It is not a physical entity and does not wear out

   • Failures occur without advanced warning

   • Can be changed quickly and easily

   • Seemingly insignificant changes code can create unexpected
     and very significant problems elsewhere in the software
     program




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  Software:
   a “trivial” example…




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