Biological Evaluation 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.”
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 Need to Test
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 demonstrateable history of use in a specific role that is the same as that of the device under design.”
Similarly, in General Program Memorandum, #G95-1 the U.S. FDA describes “…materials that have been well characterized chemically and physically in the published literature and have a long history of safe use.”
Further, sub-clause 3.8 of ISO 10993 is intended to “avoid the need for redundant experiments when information about the material and/or device is available from other sources.”
Where material testing may be a consideration, section 5.1 paragraph 6 allows that test procedures shall take into account “existing information based in the literature, experience and non-clinical tests.”
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
Surface Contacting Devices
Most medical cable assemblies 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.
Using Flow chart may help determine if material meets biocompatibility requirements
At Affinity we commonly use a flow chart to help evaluate whether biocompatibility testing is required. The chart we use is similar to that found in ISO 10993 part 1, but is 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 used in 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 similar
- 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 and do not need further testing.
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
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 can be added to resins so that the material will meet UL 94 flammability requirements. However, once added the material will 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 within the jacket without concern.
Affinity has the 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.
Eric Schnitzler, Affinity First Shift
Eric joined the Affinity team as Production Supervisor in 2006 when the company had about 70 employees. Today, he is the most senior of the four Production Supervisors who lead Affinity’s 240 employees.
Shortly after completing his duty in the United States Army as a helicopter crew chief and co-pilot, Eric began a twenty-five year career in aerospace manufacturing. During this time his primary focus was team leadership and supervision but Eric also gained valuable experience in Lean Manufacturing and ISO certification.
Eric is one of two first-shift supervisors. He supervises approximately 55 production team members, overseeing some of the more challenging products manufactured by Affinity. To make sure orders are completed on-time, Eric works closely with the production planning, quality, engineering and Customer Care. “We all work very hard to make sure our quality is 100% and that shipments to our customers are on-time,” said Eric.
When asked what he likes most about his job at Affinity, Eric said, “We have a great team and I love the challenge of producing consistently high quality products. I want our OEM customers to be completely happy and satisfied.”
Eric received his BA in Business Management from the University of Phoenix and also holds an Associate Degree in Aircraft Technology.
Eric Schnitzler works with production
team member Sam Serrato
Eric hiking in the snow
at 10,800 ft on Mt Charlton
Eric’s son and daughter, Garrett and Kasaundra, both attend Saddleback College where they are studying economics and fashion, respectively. Both have chosen business management as their minors. Garrett has been accepted to Cal State University at Fullerton where he will continue studying economics.
Eric is an avid hiker and is currently training for a “rim-to-rim-to-rim hike” of the Grand Canyon in May and for a summit attempt of Mt. Shasta in July. He also attends Saddleback College, studying classical guitar at an intermediate level and is mid-way through a 30-week family counseling course offered by Saddleback Church
Besides hiking, Eric enjoys yoga, sailing on Like Mission Viejo, swimming and cycling. Eric has swum 3 miles in 2 hours and 30 minutes and has biked 37 miles in 3 hours. He is a very active guy!
Affinity uses and stocks over 200
different cable configurations
Affinity manufactures medical cable assemblies, not cable material. “Companies that extrude their own cable may be thought to have an advantage, but we don’t think so,” said Bob Frank, Affinity’s Director of Engineering.
Rather than manufacturing “raw” cable, Affinity partners with about a dozen of the premier cable extruders around the world. Experience has shown us that no one cable manufacturer excels at all of the different configurations of cable material that Affinity uses.
Several of our cable partners specialize in complex cable configurations – those with multiple sub-cables, while others specialize in lower cost simple cable designs. Affinity works with a foreign supplier for much of our reinforced tinsel wire and a local supplier for most of our bonded ribbon-style wire.
Example of a custom
Affinity is often asked to take over manufacturing of mature cable assemblies where materials have already been specified. In these situations Affinity will use materials and suppliers that have already been selected and approved for the project.
“We have a great group of cable partners,” said Bob. “We have worked with a few since founding Affinity and others for only the past few years. Each brings unique capabilities that benefit our OEM customers.”
Whether you are developing a new custom cable assembly or are looking for an alternate manufacturing partner, Affinity can help with the design and specification of cable material.
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