Staying Connected - August 2008

ANSI/AAMI EC53 – A standard upon which to build

The primary purpose of EC53 was to promote patient safety by helping prevent inadvertent connection of patient leads to a power source, as well as allowing more rapid transfer of patients requiring continuous monitoring in emergency care.


ANSI/AAMI EC53 – the Standard for medical cable and leadwire assemblies

Prior to the adoption of the standard, rare, but serious, incidents occurred when patient leads with male pin connectors were inadvertently plugged into power outlets.  The primary way that EC53 addresses safety is by defining cable and leadwire connections with no exposed electrical contacts.

Equally as important as safety issues are mechanical and electrical performance requirements.  Medical cable assemblies meeting the performance requirement of the Standard offer a degree of reliability that would likely not be present otherwise.

More often than not, our OEM partners require higher performance and a greater degree of safety than the Standard requires.  Understanding the various components of the Standard facilitates establishing appropriate specifications for other types of medical cable assemblies.

Physical requirements

Mate and unmate testing at Affinity is done by hand to more
accurately reflect clinical use

To achieve safety and interchangeability goals for leadwire connection to a cable, EC53 specifies that DIN 42-802 be followed.  The DIN reference specifies pin and socket (plug and jack) dimensions as well as electrical contact setback to achieve a “touch proof” connector. 

To establish minimum physical performance of cables and leadwires, the standard contains requirements for:

  • Number of mate and unmate cycles
  • Retention force of connector
  • Flex life of various components
  • Tensile strength of connections and materials

Cleaning, disinfection and sterilization requirements are also detailed in the document.

Electrical requirements

Affinity Lab Manager Bob Evans testing for dielectric withstand

Minimum performance standards for several critical electrical requirements are defined in EC53, including:

  • Dielectric withstand, also referred to as Hipot
  • Sink current
  • Defibrillation withstand
  • Cable and leadwire noise
  • Contact resistance
  • Leadwire resistance for metallic, tinsel, and carbon materials

One significant requirement is for defibrillation withstand.  The cable assembly should help maintain the effectiveness of the pulse by not allowing current to travel up the cable and into the device.  It should also protect the device so that monitoring can continue after defibrillation.

Noise in an ECG signal may make accurate diagnosis difficult, if not impossible.  Cable and leadwire movement can generate triboelectric noise.  Triboelectric noise can occur when a cable is flexed causing the internal conductors and other components to rub together.  Emergency care and stress testing can be particularly susceptible to the generation of triboelectric noise because of movement of the cable.  The issue is addressed in EC53 by establishing a 50µV maximum for noise and also a standard test method to measure noise.

Testing

Finally, EC53 provides test methods and procedures by which compliance to the Standard can be verified.  Test equipment, test circuits, and specific procedures are provided to allow uniform and consistent testing.  Affinity Medical’s in-house engineering lab is staffed and equipped to perform all tests associated with the Standard.

Drop test to confirm low noise properties of raw cable material

Similarly, procedures for complying with cleaning, disinfection and chemical resistance are specified by EC53.  At Affinity, cable assemblies are typically preconditioned prior to testing to help ensure test results mirror conditions found during clinical use.  Except for sterilization, preconditioning is done in Affinity’s lab.

EC53 Rationale

An annex to the specification provides the rationale for the development of the Standard and the various provisions.  Why a requirement was included in the Standard and the benefit from compliance are detailed.

Beyond EC53

While ANSI/AAMI EC53 pertains specifically to ECG cables and leadwires, it is often used as the basis to establish performance requirements for other medical cables.  Part of the design and development process at Affinity is to work with our customers to review and apply applicable electrical and mechanical requirements of EC53 to their medical cable design.

Depending upon the application, elements of EC53 may be either more or less stringent than the clinical application requires.  As an example, EC53 calls for a minimum of 1,000 mate and unmate cycles.  We recently completed a project where the cable was designed to be connected to the device and possibly never be removed.  Testing to 300 mate and unmate cycles was neither reasonable nor required.  On the opposite end of the spectrum, another project involved a cable that would be implanted and was expected to function for five years or longer.  The 1,000 flex cycles required by EC53 were well short of the customer’s requirement of 250,000 flex cycles!

Bob Frank was a member of the AAMI Working Group that
developed the EC53 Standard

Bob Frank, Affinity Medical’s Director of Engineering, was a member of the AAMI Working Group that developed the EC53 Standard.  Affinity Medical’s knowledge and experience can help shorten the design and development process by understanding which elements of the Standard are relevant to your application. 

Involving Affinity engineers early in the design process can help achieve the desired results with an efficient design that meets applicable standards and regulatory requirements.

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Meet Matthew Pathmajeyan – Project Engineer

Although Matt Pathmajeyan is the “new kid on the block” at Affinity Medical Technologies, coming on board only 6 months ago, he has quickly taken on several new engineering projects for our customers and adjusted to the fast pace of Affinity’s engineering environment.

Matt Pathmajeyan – newest member of Affinity’s engineering team in the plant

Matt became acquainted with and acquired skills in the mold design industry at a young age while working at his father’s company during high school.  He attended Cal State Long Beach where he pursued a degree in Mechanical Engineering.  After university, Matt was hired by Gish Biomedical as an R & D Engineer.  He later joined B. Braun as a Project Engineer until accepting the offer from Affinity Medical earlier this year. 

As a Project Engineer at Affinity Medical, Matt interfaces with customers daily.  “Our projects generally involve getting regular input from our customers and feeding design concepts back to them,” said Matt.  His extensive background in tool design enables him to not only design the components, but the tooling also.

When asked what he likes most about his job at Affinity, Matt replied; “I enjoy the creative side of design where I envision, develop and produce the product.  Since Affinity Medical Technologies is a small, family owned business, I feel right at home.  It reminds me a bit of working for my Dad many years ago. I look forward to a long and productive career at Affinity Medical.”

Matt conferring with Affinity’s Director of Engineering, Bob Frank

Matt spends much of his personal time involved in music, performing as well as mixing and recording.  He plays guitar, keyboard and drums and is a member of a local band named “Versus Versa”. Matt’s group has played various musical venues including the Troubadour and Whiskey-A-Go Go in Los Angeles and closer to his home, the Orange County Fair.  You can hear a sampling of their music at: http://www.myspace.com/versusversa.  Someday we just might see Matt and his band on “America’s Got Talent” but we already know that Affinity Medical gained engineering talent when Matt Pathmajeyan joined the team.

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Overmolded Electronics

One of the unique capabilities of Affinity Medical Technologies is to mold over electronics and incorporate them into a cable assembly.

Circuit in bottom half of ABS case prior to first mold shot

Overmolded electronics package

If the need arises to add electronic circuitry to a medical device without redesigning the device itself, consider adding the electronics as part of a cable assembly.  Or, if extra capabilities need to be added to a legacy device, consider an external solution.

PCB terminated to cable after first molding operation

Finished assembly after outer molding

Affinity can help you design an electronics package that can be incorporated into a custom medical cable.  Photos show examples of our capability to overmold electronics.  Besides overmolding, we have experience with designs that are encapsulated in plastic shells and then ultrasonically welded.

The experience of our engineering team can help shorten your product development cycle.  We know what materials to use and how to position components to survive the temperatures and pressures of injection molding.

Overmolded electronics package with two D-sub connectors

If you would like to see a sample of electronics that have been incorporated into a cable assembly, contact Affinity Medical Customer Care at 949-477-9495 or email to customercare2@affinitymed.com.

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Announcements, Information and Trivia

Labor Day

Labor Day is a federal holiday in the United States that takes place on the first Monday in September.  The holiday began in 1882, originating from a desire by the Central Labor Union to create a day off for working men and women.  Labor Day is celebrated as a day of rest and relaxation which symbolically marks the end of summer.  We hope you enjoy your day off!

Affinity will be closed on Monday, September 1st in honor of Labor Day.

Affinity Customer Care - Hours of Operation

Affinity Medical Technologies customer care specialists are available from 7:00 A.M. until 4:00 P.M. Pacific Time.  You may reach all Affinity team members by phone or by email.  Email addresses are first initial followed by last name @affinitymed.com.


Suzann Sitka and Candy Golding the Affinity Customer Care team

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Affinity Medical Technologies

1732 Reynolds Ave
Irvine, CA 92614  USA
Phone: 949-477-9495
Fax: 949-477-9499
Email: CustomerCare2@affinitymed.com
Website: www.affinitymed.com