Anatomy of a Patient Cable
Medical patient cable assemblies typically consist of only a few components: connectors, yokes, snaps, cable and wire. Understanding some of the options available for these components may give you greater freedom when contemplating or designing a new cable.
Device-end Connector – is the connector that plugs into the monitor or other medical device. A wide variety of options are available including:
- Off-the-shelf Connector – available from a number of manufacturers. Typically requires no investment in tooling, but offers no option for customization. A stock connector requires the design to conform to the connector which can limit design options.
Hypertronics D02 connector with overmolded grip and strain relief
– a Hybrid connector
- Hybrid Connector – an off-the-shelf connector that has been overmolded for a custom feel and look. Overmolding, rather than using a pre-manufactured strain relief or boot, typically improves flex performance and moisture resistance.
- Custom Connector – a fully custom connector can be designed to exactly match the requirements of the cable. While there can be a substantial investment in engineering and tooling, the cost per connector can often be much lower than an off-the-shelf connector. In addition, logos or branding can easily be incorporated into a custom connector.
Example of a custom 17-pin medical connector
Strain Relief – also called a bend relief – is the transition from a connector, yoke, or sensor to a cable or wire material. Strain reliefs can be pre-formed, as is offered by connector manufacturers, or custom molded, which typically offers greater effectiveness. Strain reliefs can be segmented or smooth, with smooth being easier to clean but not providing as much bend relief as a segmented design. For applications requiring very high flex life, proper design and manufacturing are essential to achieving the specified results.
A segmented strain relief typically provides the greatest flex life performance.
Cable Material - is the “heart” of any cable assembly. It carries the electrical signals for which the cable is designed. Besides carrying signals, the feel of the cable assembly is largely determined by the cable material. How the cable feels to the user is influenced by the jacket material, including durometer (hardness or softness) and texture, and by the flexibility of the cable.
- Jacket material – most medical cables use material that meets FDA biocompatibility and cytotoxicity requirements. Two common jacket materials that meet these requirements are Santoprene and polyurethane. Both are available to meet USP class 6, meaning that they are implantable. Jacket material, thickness and durometer all affect the feel of the cable and influence flexibility.
- Insulation material - can be an important consideration when UL or CSA listing is required. The insulation material can also affect the flex and triboelectric noise characteristics of a cable.
- Conductor material and size – for most cables tinned copper is the material of choice. If high flex life is needed, other alloys are available with much higher flex life characteristics.
- Solid vs. stranded – virtually all medical cables use stranded conductors, but the same gauge conductor may have different number of strands. Standard 26 AWG wire may be made up of:
Number of Strands
Gauge of Each Strand
The higher the number of strands, the greater the flexibility of the conductor. The trade-off is that a higher number of strands increases the conductor diameter slightly and also may increase the cost.
- Fillers – often added to “round-out” cable. Commonly used filler materials are: cotton, vinyl, jute, polyethylene. Fillers typically have little or no effect on cable performance or flexibility.
- Serves and tapes – materials spirally wound around cable components to hold them in position for subsequent processing. The tightness or looseness of the wind can affect overall diameter and flexibility.
Teflon serve and spiral wrapped shield
- Shielding - can have a significant effect on cable performance. A spiral shield is typically the most flexible. However, a spiral shield may separate with continued flexing, reducing the effectiveness of the shield. Braided shields typically offer the greatest amount of shielding, but flexibility can be compromised when coverage is high,. A foil shield, which is typically aluminum laminated to a film, offers reduced flex life but is the least costly shielding method.
Example of a one-piece yoke.
Trunk cable enters at bottom and 5 leadwires exit at the top.
Yoke – typically acts as transition point from the main or trunk cable to leadwires or subsidiary cabling. Yokes can contain electronic components such as circuit boards and resistors. At Affinity we use a two-step process to overmold yokes. The first molding is done with a hard, strong material such as polypropylene. For the outer molding, a softer material such as Santoprene or polyurethane is used, giving the yoke a good tactile feel.
Patient End Connector –patient cable assemblies carry a signal between the patient and the diagnostic or therapeutic device to which they are connected. The most common connection if probably a female snap connector designed to mate with the studs on electrode patches. Other connections receive signals from sensors to measure parameters such as oxygen saturation or blood pressure, while others carry signals to devices like catheters or ventricular assist pumps.
The Snap – one of the most common ends of a patient cable.
Snaps onto the stud of a standard medical electrode patch.
Compared to the devices they are often connected to, patient cables are relatively simple medical instruments. However, engineering a long-lasting, high performance cable entails many decisions. Involving Affinity engineers early in the design process can help you achieve your goals with an efficient design that is easily manufactured at a reasonable cost.
Kevin Kom, Affinity Manager of Manufacturing and Facilities
As Affinity Medical Technologies moved into 11 years of operation in May, Kevin Kom, Manager of Manufacturing, celebrated 11 years with Affinity. In fact, Kevin was the first employee hired by company founders Mary Phillipp and Bob Frank.
Kevin’s experience manufacturing medical cables goes back over eleven years, working with Mary and Bob at Tronomed where he was Supervisor of Facilities and Molding. Tronomed was a medical cable manufacturer that was acquired by a larger company which eventually moved production out of the state.
When Kevin joined Affinity, his first job was to move the fledgling company from its 400 square foot start-up offices to its first 5,000 square foot production facility. When asked about his early responsibilities, Kevin replied “I was responsible for just about everything except engineering, finance and sales! It seems like only yesterday that Bob and I were setting up the production area.”
Kevin–an expert at insert molding
sets up one of Affinity’s presses
Kevin says that he learned early in his career that understanding tool design and the machinist’s role is important to successfully manufacture molded parts. Kevin’s background in equipment maintenance has allowed him to implement systems that have resulted in Affinity operating with literally zero equipment down time. His extensive cable manufacturing experience and expertise is a reliable and tremendously valuable asset to Affinity and our customers!
Kevin was a key member of the Affinity team that achieved ISO certification only nine months after beginning operation. He is also responsible for Affinity’s outstanding on-time delivery performance (99.2 percent average January – June 2008) and works closely with engineering, planning and sales/customer care to meet each customer’s required ship date.
“Kevin knows every cable that we build like it is his own child. He is familiar with every component and the steps it takes to build the cable,” commented Affinity Business Development Manager Hank Mancini. “Kevin is aware of every cable that is on the production floor, what stage it is at, and when the cables will be ready to ship.”
When asked what he likes best about being part of Affinity he replied “I love being part of a team that gets along and gets things done. Mary and Bob set such a high standard for integrity that there’s just no internal politics. It makes working here fun.”
As Plant Manager, safety is one of Kevin’s responsibilities
Kevin was born and raised in Southern Idaho. When he relocated to Southern California in 1984 he said “I had never seen a city larger than Boise Idaho. I liked the weather in Southern California and I also liked the faster pace of life.”
When not working at Affinity, Kevin is very involved in soccer and football with his two children, Katie and Tyler. Kevin and his wife, Davina, also enjoy taking family vacations and camping trips. He works the family vegetable garden faithfully which produces a bountiful crop of tomatoes, zucchini and other delights. Kevin is a lifelong and avid fisherman, something he says he “learned from his Dad.”
As often happens, customers ask Affinity to quote on a cable design already in production. Nearly as often, we are unable to lower costs enough using the current design to motivate the customer to change manufacturers. This was the case with this customer when we asked if they would consider a new design.
Original off-the-shelf in-line connector pair
The design brought to Affinity used two off-the shelf in-line connectors. While functional, the connectors were larger than needed for the application, did not match the design of the customer’s equipment and were costly. Preliminary discussions led to a proposal to redesign the in-line connectors; reducing the size, matching the color scheme of the monitor, and also reducing the cost of the cable assembly.
During the design process, we solicited input from the customer asking what the ideal connector would look like. Shortcomings with the existing product were documented and became part of the design input. Affinity’s proposal to redesign the products was accepted even though it would require an investment by the customer in custom tooling.
Affinity designed in-line custom connectors – higher performance with reduced cost
The final design met each of the customer’s documented requirements, offered additional functionality, and was lower in cost than using the stock connectors. It also had greater visual appeal.
Features of the new in-line connector pair were the ability to mate the connectors blindly. The “D” shape facilitated this requirement and also allowed a surface for the customer’s logo.
New custom connectors mate blindly and are strong enough
to withstand roll over by hospital bed
An additional requirement was that the force to unmate the two connectors was between 4 and 8 pounds. Tooling was designed so that as metal was removed, the mate/unmate force could be increased until it reached the desired level.
The application for this cable was such that it would often be on the floor leading to the requirement that the connectors withstand roll-over by a hospital bed. The finished connector pair was designed to survive being rolled over by a caster on a hospital bed.
For more information on how we can help solve your medical interconnect problems or for samples of this or other cables produced by Affinity, contact Customer Care at 949-477-9495 or email to email@example.com
Summertime Dining in July
With the 4th of July holiday behind us, take a day to enjoy the summer weather by dining al fresco with a casual picnic or a more elegant table setting. Whatever the plan, your family and friends will appreciate lighter style food and lively conversation in the outdoors.
In England, the Speaker of the House is not allowed to speak. The Speaker presides over the House's debates, determining which members may speak!
At the time of the attack on Pearl Harbor, the top U.S. Navy command was called CINCUS (pronounced sink us)!
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.
Suzann Sitka and Candy Golding the Affinity Customer Care team