Tackling medical interconnect

Medtech is continuously evolving, and like virtually all technology applications, is being disrupted by advances in computation, interfacing, and connectivity. Wireless/wired connectivity and edge computing/processing capability enable new applications or enhance existing applications for a range of industrial applications; the same goes for medical devices. However, medical technology standards often lead to hurdles for medtech manufacturers to overcome.

Wireless technologies still require wired connections internal to the devices, which are often extremely space constrained and necessitate unique solutions for efficient and reliable interconnect routing and attachment to meet the stiff requirements of medtech standards. Requirements include the ability to be flexible, withstand the high temperatures and harsh chemicals required for sterilization, and adhering to patient safety standards.

Custom cables

Medical cable assemblies are needed to connect power and/or analog/digital data signals between medical and laboratory equipment. Often the cables are required to have abrasion-resistant jacketing materials that provide high mechanical durability and low surface friction. Flexibility is also a frequent requirement for medical cable assemblies to mitigate kinking. In cases where autoclave sterilization is required, high temperature range cable materials are also needed.

Medical cable assemblies are generally required to meet certain application-specific regulatory and safety standards that are also regionally based. An example is ISO 10993-1, “Biological evaluation of medical devices - Part 1: Evaluation and testing within a risk management process.” In instances where the cable jacketing may come into physical contact with a patient, it’s often essential to ensure the cable jacketing is made of biocompatible materials.

Medical cable assembly categories

This can be broken down into three main categories: patient, communication, and equipment/sub-assembly interfaces. Patient interfaces are often the most regulated and constrained by safety considerations.

Equipment/sub-assembly interfaces are typically assembled as part of the original equipment and are only accessible with some equipment disassembly. The interfaces usually only interact during original assembly, repair/troubleshooting, or during upgrades/retrofitting. This includes power, display, accessory, and often custom cable assemblies used to combat unique interconnect/routing challenges during product development, repair, or upgrade.

Several types of communication interfaces are used in modern medical equipment/devices. Higher speed and density digital interconnects, such as USB, Ethernet (RJ45), and even fiber optics are becoming increasingly common. Older serial or parallel communication cable types, such as RS232/422/423/485 and Phone Cables (RJ11) are also common on many older and long product series equipment/devices striving to be backwards compatible with legacy accessories.

Patient interface cables are made of highly durable cable types and must be replaced at regular intervals several times throughout the life of the medical device. The cables may be replaced due to upgrades from the manufacturer for performance or to address issues discovered after product deployment. The types may be long-life, limited-use, or even single-use/disposable interface cable assemblies.

Long-life medical cable assemblies are the most durable, wear-resistant, and flexible type. Limited-use cable assemblies, which may include ECG diagnostic leads and ICU/CCU monitor cables, are often damaged during regular use. This can be a result of high mechanical stresses, exposure to harsh cleaning chemicals, or even intended obsolescence. The cables must be replaced at regular intervals or when the cable assembly exhibits signs of wear. Single-use cable assemblies are discharged after use instead of being cleaned and reused. This category often includes test leads/lead sets, fetal monitoring cables, electro-surgical device/accessory cables, and catheters.

Custom cable assemblies

During the development of medical equipment and devices, cable interconnect, and routing is often a late-stage consideration. This situation is often necessary as solving the latest medical technology challenges and being competitive often requires innovation and diverse engineering methods. It’s not unusual for medtech designers to run into situations where standard interconnect cables can’t fit in the available space or don’t yield the desired level of safety with off-the-shelf cable assemblies.

A custom cable connector and/or connector overmold may be an ideal solution preventing costly redesign of the housing or sub-assemblies. If there’s too little clearance to allow for reliably connecting a plug-in style connector into a sub-assembly port within a device, a right-angle connector head could allow for the necessary clearance and greater reliability of the connection long-term. Exposed conductive surfaces at the connector points could lead to operator shock or even electrostatic discharge (ESD) concerns in damaging the interface. Custom connectors overmolds could provide the necessary insulation without redesigning the interface and at a fraction of the time and cost.

There may also be less dramatic instances where a medtech original equipment manufacturer (OEM) may not offer a cable short enough or long enough to satisfy the needs of a given application. In some cases, a cable could be too long, and a shorter cable could provide electrical benefits or prevent tripping/entanglement hazards. In other cases a longer cable could provide enhanced operator safety, ability to place the device more optimally, or preemptively allow for the need to reposition equipment without the need to purchase longer cables.

Another common instance is legacy medical equipment/devices may use older styles of connector interfaces or cable types, where more advanced or beneficial types are now available. The solution may be retrofitting the legacy device. It may be more cost effective and quicker to have a custom cable with a legacy interface on one end and a more desirable interface on the other or have a newer or different cable type. This type of customization could lead to substantial cost/time savings, especially if the cable interface is frequently cycled.

After determining the requirements for a cable assembly for a medical technology, there are circumstances where a suitable cable assembly is available off-the-shelf. This is rarely the case so custom cable assembly fabricators help to solve this challenge. Not all custom cable fabricators have the expertise or capability to manufacture medical-grade cable assemblies so choosing the right partner makes the difference.

About the author: Steve Ellis is the director of product strategy at Infinite Electronics Inc.

Infinite Electronics Inc.
https://www.infiniteelectronics.com