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Design of a Malignant Hyperthermia Susceptibility
Screening Device
Sara DollLisa KaczmarskiPhilip Magcalas
Department of AnesthesiologyChildren’s Hospital of Pittsburgh
University of PittsburghSenior Design – BioE1161
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Overview-The Problem
Malignant Hyperthermia (MH) is a chain reaction event wherein susceptible patients, when administered common gas anesthetics, undergo drastic physiological changes.
• greatly increased body metabolism
• muscle rigidity
• fever up to or beyond 43°C
There are currently no standard devices or procedures in common practice to screen the general population for this condition.
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Overview-The Solution
It is hypothesized that MH susceptible muscle, when compared to normal muscle, will be significantly different in compound muscle action potential (CMAP) and force of contraction.
The solution lies in the design of a device that restricts arm movement, while measuring the isometric force produced by the thumb when the ulnar nerve is stimulated. This may then be used to develop a standardized protocol for MHS screening.
Such a device would ultimately be beneficial to:• Anesthesiologists • Patients and their families• The general Population
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Project Goals
1. Create a device that meets design requirements
2. Test and assess the effectiveness of the final device in measuring forces within a specific range
can be easily sanitizedcan be transported with ease (lightweight)has minimal assembly or adjustment requirementscan be used with both the right and left handsmaintains the arm at the same height as the OR bed
fastens securely to bed in operating room
securely restrains the patient’s forearm and hand
comfortably accommodates 3 to 5-year-old patients
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Device Features
1- Arm board
2- Arm/hand restraints
3 – Force Transducer Mount
4 - Support
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Design Options
Materials
Board• Wood
• Metal
• Polymer
Straps• Fabrics
• Polymers
Arm/Hand Restraints• U-shaped cushions
• Adjustable straps
• Top restraint
Force Transducer Mount
Track• Integrate into board
• Attach on edge
Orientation• Left hand only
• Ambidextrous
Range of motion• Fixed
• Planar
• Angular
Support• Moveable cart
• Vises on side of OR bed
• Integrate into existing equipment• Elevator• Recess for armboard
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The Design Process
- Prototypes (3 total)
- Frequent meetings• continuous design feedback and refinement of design requirements from mentors
- Anthropometric data
- Material samples• arm board and straps
- The process of manufacturing• Carrying out reality from concept - importance of details, details, details
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The Evolution of Design
Dec.
Concept Prototype #1
Jan.
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The Evolution of Design (cont’d)
metal
Nylon Velcrostraps
rigid, 1-1/2”polymer
Flexiblepolymer
Jan.
Concept #2
Feb.
Prototype #2
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The Evolution of Design (cont’d)
Prototype #3
Mar.
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The Final Design
3 – Force Transducer Mount
2- Arm/hand restraints x 4
4 - Supportx 3
1- Arm board
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The Final Design (cont’d)
TOP BOTTOM
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Benefits of our Design
Arm board ambidextrous
sized for wide range arm/hand sizes
simple construction
Arm restraints adjustable
removable
flexible
single material, single piece
sanitizable
strong (resistance to tear)
Force Transducer Mount translation in two planes
interchangeable (support 2 diff. FT)
ambidextrous
Support integrates with existing equipment
sturdy
separable from arm board
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Benefits of our Design
Overall - Simplicity
in design
in assembly
in manufacture
- Satisfies ALL design requirements
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Competitive AnalysisCompetitors
• Halothane caffeine contracture testing (muscle biopsy segments)
Our Strengths• Non-invasive• Not necessary to wait for laboratory results• Less expensive• Quick procedure, which may be performed pre-op
Our Weaknesses• Potentially less accurate
- Not testing on actual muscle fiber- Not standardized process
Our device’s strengths outweigh the weaknesses…However
- Contingent upon accuracy of device
- Reliant upon efficiency of data acquisition program, which lies outside the scope of this project
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Other Considerations for Design
Manufacturability• Acrylic
• Workable• Cost• Durable
• SolidWorks• Ease of Use• Available• Experience
Human factors• Contextual Inquiry• Device Observation• Design Plan Assessment• Heuristic Evaluation
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Class II (moderate risk)• ‘isokinetic testing and evaluation system’ (890.1925)• contact with skin but non-invasive
No Predicate Device
Currently 510(k) and PMA exempt• Investigational device - clinical evaluation required for further
development
• IDE regulation will be required
However in the future, should the decision be made to pursue marketing this device, this will require a Class II PMA device application
Regulatory Concerns
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Constraints to Further DevelopmentRegulatory
• Again, no predicate device. Final FDA approval will be complicated
Market• Limited now to Children’s Hospital until a more
precise MH susceptible screening protocol can be established.
Economic Resources• Limited breadth of project funds
Human Resources• Time constraints of all involved
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Project Management
Our Goals What we Actually Achieved
Test and assess the effectiveness of the final device in measuring forces within a specific range
Force Transducer Calibration• Known force range• Located an amplifier • Preliminary signal processing
Waveform filteringEstablish force-voltage relationship
Build a device that: •Comfortably accommodates 3 to 5 year old patients•Ambidextrous•Fastens securely to OR bed• Can be easily sanitized and transported with little assembly•Allows for accurate measurement of contraction force and clear data interpretation
• Arm Board and Support • Currently in machining
• Overall - accomplished a simple, compact design that satisfies all design requirements
• Straps (Adjustable size)• Assembled
• Force transducer• Grass/Astromed FT03, FT10 obtained• Mounting Device Currently in machining
Device In Pre-Assembly
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Project management (cont’d)
December
- Preliminary SolidWorks drawing for armboard, support
- Order force transducer (Grass – model FT03)
January
- Gather materials for prototype
- Build initial prototype
February
- Prototype testing
- Design revisions
- Finalize SolidWorks drawing
- Order final materials
March
- Build/Assemble device
April
- Device testing, as time allows
- Draft final report and presentation
December
- Discussed device requirements with advisors
- Researched materials
February
- Design revisions
- Gathered materials for and built Prototype 2
- Prototype 2 Assessment
- Preliminary SolidWorks drawing
April
- Device machining underway
- Draft final report and presentation
March
- Ordered final materials
- Anthropometric research
- Gathered materials for and built Prototype 3
- Finalized dimensions and SolidWorks Drawings
- Submitted design to machining
January
- Gathered materials for and built Prototype 1
- Ordered force transducers (Grass FT03, FT10)
- Prototype 1 assessment
Projected Schedule Completed Schedule
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Project management (cont’d)
Who was responsible what
Sara Doll•Armboard SolidWorks•Strap SolidWorks•Concept SolidWorks•Mentor Meetings•Prototype 3
Lisa Kaczmarski•Material Research•Materials Acquisition•Contact with Suppliers•Prototype 1•Final Product (straps and armboard)
Philip Magcalas•Device Concept Drawings•Anthropometric Research•Force Transducer Mount Solid Works•Prototype 2•Final Product (FT supports)
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Acknowledgements
• Dr. Brandom’s Clinical Research Fund• Children’s Hospital of Pittsburgh
• Dr. Barbara Brandom• Dr. Robert Sclabassi• Dr. Andreas Hoyer
• Prof. Mark Gartner• Dr. Mingui Sun• Joe Beuten
• Total Plastics, Inc.
• George Kurzdorfer• University of Pittsburgh
• Department of BioEngineering
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Thank you!Questions?
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Design Details – Arm Board
H=30cmW=33cm
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Design Details - Support
H=9.8cmW=17.5cm
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Design Details – Force Trans. Mount
H=4.4cmW=10.2cm
H=7.3cmW=28.1cm
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Design Details - Straps
large
small
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