Power
Prepare for changes in medical power standards
The increased focus on technology for medical treatment and for the improvement of personal wellness overall is bringing new suppliers into the orbit of the increasingly stringent regulation that governments have introduced to maintain user and operator safety. Philip Lechner, product marketing, power, Avnet Abacus, tells us more
T
he rise of the Internet of Things (IoT) in medical applications is leading to the introduction of new types of connected device that report health status and which can act on the patient. Some operate in the controlled environment of the hospital. For example, telemedicine systems are beginning to appear where the surgeon is assisted in operations by robotic machinery. Others work, mainly for monitoring purposes, in non-controlled situations such as the patient’s home. As well as safety, the connected nature of these medical devices also demands manufacturers assess the risks raised by issues of electromagnetic compatibility, to ensure that devices do not create excessive emissions or are affected by other electronic systems. It goes without saying that surgery carried out by robotics cannot be affected by stray wireless network signals, for example. To deal with the increasingly complex systems now being used in the medical environments, governments around the world have engaged in a process of analysis of all the standards they demand manufacturers follow. Older, more prescriptive regulations often introduced to cover specific categories of device have given way to more flexible standards that can better cope with the more complex
20 November 2016
demands of today’s often multimodal devices. A core part of every electronic medical device is the power supply. For close to four decades, when dealing with the power supply, manufacturers of medical devices and systems around the world have worked to the IEC 60601 standard. Since the standard’s initial publication in 1977, it has received three major revisions with a fourth now in progress. Initially, IEC 60601 focused on “basic safety” – ensuring that the product could not cause injury through electric shocks or short-circuits if it malfunctioned. Later changes expanded the scope of the standard to cover situations where power problems may compromise the “essential performance” of the device and cause hazards or injuries if that performance were to be compromised. With the publication of the third edition of IEC 60601, a major change of approach was introduced. The standard made effective by the European Union in 2012 and followed by Canada and the US a year later, introduced the requirement for the manufacturer of the complete medical device to perform a formal risk management that conforms to the approach set out in ISO 14971 for each device. This standard directs the
Components in Electronics
manufacturer to identify hazards associated with the medical device, assess the risk and verify that the solutions to address that risk operate over all stages of the product’s life cycle. However, the risk management defined in IEC 60601 is restricted to ensuring basic safety and essential performance requirements. The risk management needs to encompass not only the end- product manufacturer’s processes and designs but also those of suppliers of subsystems such as power supplies. The third edition also changed the classifications of electrical contact with patient and operator to support the risk-analysis procedures of ISO 14971 and to define different protections for patients and operators. Early editions of IEC 60601 defined three types of system that would determine the approaches needed to determine safe operation. Type B, for Body, was defined for devices that had no electrical contact with the patient. Type BF (Body Floating) is for equipment with a floating electrical connection to the patient, but not direct to the heart. The third, Type CF (Cardiac Floating), is reserved for the subset of equipment that does provide a floating electrical connection to the heart. In the third edition, the means of
protection (MOP) requirement defines parameters such as the level of isolation between electrically charged circuitry, any equipment that may come in contact with the device and the people around it. The level of protection for power supplies determines factors such as creepage and clearance distances, insulation and protective earth connections. There are sublevels for each of the two forms of MOP. For example, a system that the risk assessment determines should be level two for means of operator protection (MOOP) should have isolation of 3000V AC with a creepage distance of 5mm. A system that risk assessment determines can be more relaxed, and so fit into the level- one MOOP classification, would be expected to have isolation of 1500V AC and a creepage distance of 2.5mm. The result of this shift to conformance with the third edition of IEC 60601 has been to increase the level of cooperation between power supply and equipment manufacturers to guarantee the final equipment has the appropriate level of safety protections for both patients and operators.
Another shift is underway following the publication in 2014 of the fourth edition of
IEC 60601. In late 2014, the US FDA issued a guidance note recommending to manufacturers that they start developing and testing medical products to the fourth edition in expectation of a change in regulations within several years. The fourth edition of IEC 60601 contains a number of changes. There are new immunity requirements for EMC and the revised version calls for more robust risk analysis. As well as taking into account immunity of radiated and conducted electromagnetic emissions the fourth edition calls for resistance to significant increases in electrostatic discharge (ESD) levels as well as voltage dips and power interruptions. To take into account the more complex wireless communications environment around connected devices, the stipulations for immunity from RF transmissions have been tightened up – demanding higher levels of immunity from medical devices. The fourth edition takes into account
the environment in which the device is used. There are different immunity requirements depending on whether the system is used in a professional healthcare environment, such as a hospital, in the home or in more specialised locations, such as military or heavy-industrial environments. As with the efficiency regulations for external power supplies, regions around the world are adapting to the fourth edition of IEC 60601 at different rates, with the US FDA currently leading with its plan to no longer allow declarations of conformity under the third edition after the beginning of April 2017. Europe and countries in the rest of the world are expected to follow suit afterwards. However, many manufacturers will want to conform to what is currently the most stringent regime, that of the US, to ensure that they have the widest possible market for their products.
www.abacus.avnet.com www.cieonline.co.uk
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