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Norm compliance for network connections

Norm compliance for network connections Manufacturers of medical technology or IT vendors integrating applications into hospital network environments are faced with the problem of having to supply network connections that are suitable for medical devices. That is no easy job, if expensive and risky external insulators are to be avoided.

Networks in hospitals, rehabilitation centers and medical practices are constantly expanding and taking on more and more devices. The aim is to improve efficiency in the whole clinic process flow by means of integrated systems and increased communication. For example, X-Ray pictures can be transmitted to desktop PCs and even to smartphones, information from hundreds of sensors and actuators at the Point-of-Care can be accessed by workstations on the hospital wards and data from operations is stored on central servers for documentation purposes. Even the patient emergency call will in future be run over the network. There is hardly any application - and certainly not any undergoing current development - which is destined to be operated on a stand-alone basis. And the IT backbone is Ethernet-based, or wireless connections are used for mobile peripherals. That explains why an increasingly colourful jumble of conventional IT and medical technology devices is currently at large in hospitals.

Two cases need special attention when this type of hybrid networking is addressed. On the one hand, there are normal IT systems, ie central servers of workplace PCs which generally do not conform to the leakage current norms for medical devices. Medical device networks have to be protected from leakage current 'infections' via these devices. On the other hand medical devices with a network connection have to be protected from insecure networks. The established practice is that insulators are inserted between the device and the network to either protect the medical device from the network or the medical network from the simple IT system. This is an effective solution, but often one with unexpectedly high costs. More than anything this solution is quite fault-prone: if for whatever reason the insulator is forgotten between the network and the device then all protection fails. There is practically no possibility to check whether a clip-on insulator has been implemented or not in the infrastructure. So the more cost-efficient and secure solution is for the network connection of the medical device or IT system to be protected right from the word go.

When a network connection is being designed the IEC60601-1 and IEC60602-XX norms have to be adhered to - as also applies to the whole system. For example, medical technology devices have to ensure protection against 1500V by one MOOP (Means of Operator Protection) or against 2500V by two MOOPs. Two MOOPs are always necessary when the medical device is connected to a patient and a user interface is available for the doctor, attendant or patient. That is always the case for integrated devices with PC technology. Conventional LAN cards however according to IT EN 60950-1 are only guaranteed to protect against up to 1500V. So they do not meet the requirements of the medical environment. A LAN interface design which is suitable for medical devices is mandatory. When selecting the right components the list of requirements which have to be fulfilled is a long one.

The physical connection of the Ethernet connector has to have a closed housing. This is imperative as the wiring which lies between the connector and the PCB has to be dust- and dirt-proof. A large range of this type of coupler is available. However only a very small number of manufacturers guarantees the dust-proof qualities of the coupler's housing. And an Ethernet coupler which is apparently encapsulated is by no way a guarantee for long-term secure insulation.

In order to guarantee secure insulation to the board the IEC60601-1 norm states that the distance of the insulation (grounding) to the signal line in order to avoid leakage current in the air should be 4mm and on a PCB 6mm. Today, most Ethernet couplers with metallic shielding only have a pin distance of about 2mm. In addition it has to be noted that it is not a question of the distance of the pins from the centre to the centre but the pin distance between the edges of the solder contacts and the edges of the PCB tracks. The pin distance between insulation and signal line itself has to be significantly larger than 4mm. But due to the increasing miniaturisation and SMT mounting of the layouts these distances are no longer available.

It does not however suffice to use a closed, dust-resistant coupler. The coupler has to be insulated from the front panel of the component group. For this reason common couplers which end at the front panel are not suitable as they cannot comply with either the 6mm (PCB) or 4mm (air) requirements. Consequently, a coupler has to be used that protrudes out of the front panel in order to adhere to the required distance. This also applies to the Ethernet transformer. Most Ethernet transformers which are currently available in the market only have a distance of 5mm from pad to pad - due to the small form factors (SFF) trends. But 6mm is still the required distance. Therefore a suitable transformer has to be designed in.

Another feature of Ethernet interfaces which is unsuitable for IEC60601-1 compliance is the LED status display of the Ethernet connection as is built into nearly all Ethernet interfaces, at least when the LEDs have to be integrated in the coupler. This has to do with the physical size of couplers. Why? For cost purposes LEDs are galvanically coupled with the component group's grounding. And as these do not comply with the distance required to the signal leading lines you can recognise IEC60601-1 compliant Ethernet interfaces amongst other things by the fact that there are no LEDs on the connector itself. These few but essential features are important for a design-in and should not pose too large a problem. However that is not the end of the list of requirements. The construction of the coupler affects the design of the transformer. The PHY configuration also has to be adapted which would require access to the PHY chip manufacturer's NDA documents.

These necessary alterations in turn impact on the range of use, which has to be kept at 100m to comply with the Ethernet specification. Any changes made to the card have an influence on the component group's shielding which again affects ESD and EMC tests, so that producing a medical LAN card from a standard Ethernet card is in no way a straightforward issue. And while the requirements in terms of design are relatively easy to master, additional costs for certifications have to be taken into consideration. Laboratory costs for tests can be calculated at approximately €15,000, plus around €3,000 for UL listing and €5,000 for full CE certification. All in all about €18,000 have to be additionally invested just for exchanging the coupler and the transceiver in comparison to a 'normal' LAN card. So it comes as no surprise that a large number of medical devices and IT systems are still employing standard LAN cards and using external insulators, as this presents no initial costs as these investments have to date not been made by any manufacturers.

However now that the PCIe Medical LAN Card has become available from Kontron, it is possible to replace the relatively pricey tandem of a standard LAN card and external insulator with an IEC60601-1 compliant component group, which also increases the level of operational safety as unsafe network connections are eliminated.

Application areas for this new IEC60601-1 compliant PCIe Gigabit Ethernet card are clinics, rehabilitation centers, medical practices, and any scenario where medical devices have to be integrated into a network with conventional desktop PCs or high-availability archiving, backup or storage solutions. The PCIe 2.0 compliant Kontron PCIe Medical LAN Card has been designed to fit into any PCI Express x1 compatible card slot. Slot brackets for full height or low profile mounting are included in the delivery. The long-term available card has either one or two insulated Ethernet 1000Base-T interfaces via RJ45 connectors. Both versions are based on the Intel 82574L GbE controller which guarantees extremely high compatibility and high transfer rates. If a card with two Ethernet interfaces is chosen, users need no longer worry about which coupler has the insecure network connection and which has the secure one, as both are secure. The Kontron PCIe Medical LAN Card is available with immediate effect. Support is offered for all Windows operating systems starting from Windows XP/Windows 2000 and from Linux kernel 2.4.18.
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