You wake up early in the morning and unplug your smartphone only to find it has failed to charge. On the commuter train an hour later, you open your laptop but notice your charger cable has frayed. On your walk to the office, you plug your headphones into a music device, press play and realise the jack has broken. The sound crackles through one ear as you trudge down the road.

These are scenarios that many of us will have experienced before – if not necessarily all in one morning. But as irritating as they are, in most cases, they tend to cause us only minor inconveniences.

However, there is one industry in which the stakes of a failed connection are much higher: the medical device sector.

In a hospital setting, such as an intensive or cardiac care unit, the constant availability of medical devices – and the reliability of the connectors between them – can often be the difference between life and death.

But designing connectors for the medical device sector is not easy. They must be able to withstand frequent connecting and disconnecting, regular cleaning and sterilisation, and in some cases, shock and vibration.

Crossed wires

Perhaps the biggest challenge is connecting different devices together in a way that ensures patient safety. A critically ill, hospitalised patient could have as many as 40 tubes going in and out of their body at any one time, delivering drugs, nutrition and blood to their arteries, veins, stomach, lungs and other areas. Many of these connectors have similar sizes, shapes and designs, and can be easily mistaken for one another. All it takes is poor lighting, time pressure or a tired, overworked member of staff to connect two wrong devices together.

In the 1990s, the general public grew increasingly concerned as stories mounted of patients being injured and killed from misconnections. Concerns centred on medical devices fitted with luer connectors, which were invented in the late 1890s to provide leak-free connections between hypodermic syringes and needles.

In one case, reported by the New York Times in 2010, a 24-year-old mother from Kansas and her 35-weekold foetus were killed when a feeding tube was mistakenly coupled with a tube sticking into a vain.

“Putting such food directly into the bloodstream is like pouring concrete down a drain,” said the New York Times’ journalist Gardiner Harris.

The risk posed by connectors was eventually reduced when the first of a new set of standards was developed by the International Organization for Standardization in collaboration with the International Electrotechnical Commission, in 2011.

“This series aims to improve the safety of the delivery of liquid and gases in healthcare settings,” said Scott Colburn, convener of the joint working group that is developing the standards. “It draws information and inspiration from a number of international and European standards in the field, but is the first international series of standards of its kind.” The standards, some of which have not yet been published, have triggered new connector designs, and have prompted healthcare facilities and practitioners to rethink their processes as they transition away from the universal use of luer connectors.

Fail to prepare…

The US Federal Drug Agency website offers practical advice to help achieve this transition. It encourages healthcare providers to “work with suppliers to develop a plan for removing devices with old connector designs from inventory and replacing them with devices with the new connectors”, and to ensure that “all clinicians and providers are trained in advance of introducing medical devices with new connectors to avoid any interruption in therapy”.

Despite the negative public attention, the connector market has continued to grow in recent years. According to a recent report by Zion Market Research, the global market is likely to reach $2.88 billion by 2022, developing at a compound annual growth rate (CAGR) of almost 7.2% during 2017–22. Another report from MarketsandMarkets claims the sector will reach $2.69 billion by 2021, at an even higher CAGR of 10.5%.

“The major factors driving the growth of this market are increasing incidence and prevalence of chronic diseases, rapid growth in the medical devices market and growth in the home healthcare market, which results in increased adoption of miniaturised connectors and growing healthcare expenditure across the globe,” said the MarketsandMarkets report.

Great and small

Arguably the biggest recent driver of connector innovation has been the trend towards miniaturised medical devices. This includes small handheld instruments that improve diagnostic procedures, and portable medical devices, such as blood-pressure monitors and oxygen meters, than enable care to be given outside of traditional healthcare settings.

Major factors driving the growth of the connector market are increasing incidence of chronic diseases, rapid growth in the medical devices market and growth in the home healthcare market, which results in increased adoption of miniaturised.
– MarketsandMarkets report

The emergence of multitasking hybrid connectors that combine signal, power and data into one small, densely packed connector has been a chief enabler of this trend; it has helped design engineers to drive down costs, and provide more user-friendly devices for medical practitioners and patients.

One leading hybrid connector is the MediSpec Hybrid Circular MT Cable Assemblies and Receptacles for Integrated Optical and Electrical Solutions, designed by Molex. It combines optical and electrical solutions in a single connector with options for three configurable ports. It offers metal and medical-grade plastic connector housing options; one to withstand harsh environments, the other for sensitive applications, such as MRI and PET scans.

Another example is Large Format Hybrid Connector from Colder Products Company, which features multiple dry-break couplings and an easyto- use twist latch for the repeated connection of multiple lines. The product employs a single connection point for pneumatic, fluid, data and power connections, which saves space, minimises manufacturing effort and increases safety.

Advanced connector technology has also emerged to help mitigate the electromagnetic signals and interference that medical devices submit. This is particularly critical with smaller, portable devices that transmit data to healthcare providers through wireless or cabled LAN networks. Modern connectors should have sufficient shielding properties, and use materials with low magnetic fields and overmouding connector cables that can absorb disturbances.

“Filtered D-sub connectors are available with built-in filtering that minimises these dangers,” explained Ed Garstkiewicz, industry segment manager at Harting, in a recent article for Electronic Products and Technology Magazine. “They can be purchased with inductive ferrite filtering in the PCB material holding the connector pins. This cost-effective, low-level filtering has minimal insertion loss while reducing EMI emissions that might otherwise be close to the specified limit.”

Of course, designing miniaturised medical connectors isn’t easy. In an article for Electronic Component News last February, journalist Lexi Metzler identified several challenges.

“Pin density and configuration must consider proper connector spacing,” he said. “Improper spacing could lead to issues with the data transmission from interference between functions. When it comes to small connectors, a common problem is when the cable is too big for a connector. In addition, sufficient creepage and clearance must be maintained between connector contacts to enable them to safely carry higher voltage signals, in accordance with ISO 14971. Too much power through a small contact can cause connector failures.”

Interconnects with exposed electrical contacts have to be sealed from the sterilisation environment, so having the whole connector enclosed and sealed would be advantageous.
– Justin Kennedy, TE Medical

Tackle the source of the problem

Even these innovative connector designs may seem overly intricate in the not-too-distant future as wireless technology becomes increasingly popular. One recent development in this direction is the contactless connector, which transfers power via inductive coupling, and therefore has no exposed electrical parts.

“Interconnects with exposed electrical contacts have to be sealed from the sterilisation environment, so having the whole connector enclosed and sealed would be advantageous,” Justin Kennedy, director of product strategy at TE Medical, told Medical Device and Diagnostic Industry.

With so many options on offer, choosing the right connector supplier is a difficult task for medical device OEMs. A key piece of advice is that no one size fits all. Connector materials, for example, will vary in quality, durability and the number of connecting cycles they are able to perform. The trick, according to industry leaders, is picking a connector that fits the needs of the specific medical application from a reputable supplier, and forming a close relationship with that supplier.