Staying Connected - March 2010

Biocompatibility of Materials used in Medical Cables


ISO 10993 is widely accepted as the standard
for biological evaluation of medical devices

ISO 10993 and FDA regulations call for materials used in medical devices which come in contact with the body to be biocompatible.  Dorland’s Medical Dictionary defines biocompatible as “The quality of not having toxic or injurious effects on biological systems.”

Non-contacting Devices

Medical devices that do not contact the patient’s body directly or indirectly are considered “non-contact devices” and are not included in the scope of ISO 10993.  There are no requirements to use biocompatible materials for non-contact devices.

Evaluating Testing Requirements

Within ISO 10993 part one, sub-clause 3.6 states “Evaluation may include both a study of relevant experience and actual testing.  Such an evaluation may result in the conclusion that no testing is needed if the material has a demonstrable history of use in a specific role that is the same as that of the device under design.”

Further, sub-clause 3.8 of the standard is intended to “avoid the need for redundant experiments when information about the material and/or device is available from other sources.”

The Affinity engineering team typically attempts to use materials that can be shown to have had a long and safe history of use.  This reduces or eliminates the need for biocompatibility testing which helps reduce development costs and can shorten a project timeline.


Most medical cable assemblies
can be considered surface
contacting devices under ISO 10993

Most cable assemblies that Affinity currently produces are considered surface contacting devices under ISO 10993 section 4.2.2.  Further characterization by duration of contact under section 4.3 would indicate that most medical cable and leads would be classified as “limited exposure,” having bodily contact not greater than 24 hours.

Where material testing may be considered, section 5.1 paragraph 6 allows that test procedures shall take into account “existing information based in the literature, experience and non-clinical tests.”

Flow Chart

At Affinity we commonly use a flow chart to help evaluate whether biocompatibility testing is required or not.  The chart we use is similar to that found in ISO 10993 part 1, but tailored to the materials commonly used in the manufacture of medical cables and connectors.


Affinity manufactures a variety of
cables for our OEM partners that are
classified as “non-contact devices

Using the flow chart, the first question is “does the cable come in contact with the body?”  If it does not, no further evaluation is necessary.

If the cable assembly or lead will come in contact with the body, additional questions may help evaluate whether biocompatibility testing is required:

  • Is the material the same as a marketed device
  • Is the manufacturing process the same
  • Does the material have the same chemical composition
  • Is the type and duration of body contact the same
  • Will the same sterilization method be used

If the answer to all of the questions is “yes,” it can then be concluded that biocompatibility requirements for the cable assembly or connector have been met and testing is not required.

If the answer to any of the above questions is “no,” additional evaluations may be required.  If acceptable justification to use the material or test data exists, testing may be avoided and the material may be considered to meet biocompatibility requirements.

As an example, medical grades of Santoprene® thermoplastic elastomer have a DMF (drug master file) lodged with the U.S. F.D.A., and are approved to USP Class VI Part XXIII.  When referenced, this information can lead to the conclusion that these materials meet ISO 10993 biocompatibility requirements.

If acceptable justification or test data is not available, consultation with a toxicologist may be required.


Independent laboratories offer
various degrees of
biocompatibility testing services

Biocompatibility Testing

For medical devices with only surface contact and contact duration of less than 30 days, typical of a medical cable assembly or leadwire, ISO 10993 section 1 indicates that testing shall included cytotoxicity, sensitization and irritation or intracutaneous reactivity.

For cables assemblies that will come in contact with blood or tissue, a higher level of biocompatibility testing may be required.  And, if the cable will be implanted or have prolonged contact (greater than 24 hours) with blood or tissue, extensive testing will likely be required.

Flame Retardants

Flame retardants can be added to most plastics so that the material will meet UL 94 flammability requirements.   However, most of the additives will then cause the material to not meet ISO 10993 biocompatibility requirements.

For a cable assembly, only the outer jacket typically comes in contact with the body.  Materials that do not meet biocompatibility requirements, such as those with flame retardant additives, can be used if contained within the jacket.

Summary

Affinity has experience and expertise to help guide our OEM partners in selecting appropriate materials for use in medical cable assemblies.  We also offer our assistance in determining what biocompatibility testing, if any, may be required for the device being considered.

For additional information or to discuss any aspect of medical cable design, including the use of biocompatible materials, please contact the Affinity Engineering Team.

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Meet Jerry Ruiz – Affinity 2nd Shift Supervisor


Affinity Second Shift

Jerry Ruiz joined Affinity Medical in October 2009 as second shift supervisor filling a vital need as production increased.  Before finding a home at Affinity Jerry was a Production Manager for Irvine Electronics, working on projects for N.A.S.A. (the Space shuttle), Boeing, and other military applications.  Previously, he had been a Quality Control Supervisor at Selco Products -Electronic Controls and also a Production Manager.

After leaving the Navy, Jerry bought his first home in Laguna Niguel then move to Huntington Beach where he now lives.  Jerry’s daughter is in her first year at San Francisco State University.  This fall she will be transferring closer to home to Long Beach State University and will be majoring in Business Marketing.


Jerry supervising
2nd shift production

Jerry enjoys outdoor activities including riding motorcycles in the many canyons in Southern California.  He also enjoys sky diving and anything to do with water sports.  He also says he enjoys “just kicking back and enjoying life. After all, we only have one.  I like spending time with my family and friends.  We love vacationing in Hawaii - any island - from the big island, Maui, Molokai, Oahu, and my favorite, Kauai.  Aloha.”

When asked what he hoped to accomplish at Affinity, Jerry replied: “To help make Affinity Medical Technologies the number one medical cable manufacturer in the USA.”  With team members like Jerry, Affinity is well on its way to reaching his goal.

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Tinsel Wire


Micro photo of tinsel wire –
flattened conductors wrapped
spirally around a strong fabric core

Where high tensile strength and a high degree of flexibility are required for medical leads, tinsel wire is commonly used.

Tinsel wire is made by flattening the conductor material into a ribbon and then spirally wrapping one or more conductors around a strong fabric core.  Tinsel conductors are typically copper and are often plated with tin or silver.  This type of wire construction offers excellent flexibility due to the ribbon conductors and excellent tensile strength due to the strong fabric core.

One of the core competencies at Affinity is terminating tinsel conductors.  We employ proprietary methods to assure an optimal electrical connection while maintaining a high strength termination.

Tinsel wire is more costly than ordinary stranded copper wire because the materials are more expensive and the manufacturing process is more complex.  However in applications where both high flex life and tensile strength is required, tinsel wire or cable made up of tinsel conductors may be the optimal design choice.

 

Announcements, Information, and Trivia

Pencil with Eraser – We may take for granted the invention of Hymen Lipman.  In 1858 he registered the first patent for a pencil with an attached eraser - U.S. Patent #19783, which allowed a user to make a mistake and easily correct it.

747 – The Boeing 747 Jumbo Jet was the world's first “jumbo jet” and the largest passenger jet from 1970 until 2005.  Boeing has manufactured over 1,360 747’s and the 400-series is the world's fastest operating airliner with a cruise speed of 567 mph and a range of over 8,300 miles, a third of the distance around the globe!



Suzann Sitka, Cesar Jara and Candy Golding
- the Affinity Customer Care Team

Affinity Customer Care -
Hours of Operation

Affinity Medical Technologies customer care specialists are available to assist you from 7:00 A.M. until 4:00 P.M., U.S. Pacific Time, except holidays.

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Affinity Medical Technologies

1732 Reynolds Ave
Irvine, CA 92614  USA
Phone: +1 949 477 9495
Fax: +1 949 477 9499
Email: CustomerCare2@affinitymed.com
Website: www.affinitymed.com