No matter what kind of medical device you are working on, there are some general requirements related to safety which will apply to your medical device, or the development process of that device. This article will introduce the general safety requirements, as defined by IEC 60601-1.
The design of your medical device must meet these requirements in both ‘normal use’ and in ‘reasonably foreseeable misuse’. To learn more about what this means for your medical device, take a look at the short course below.
What is considered reasonably foreseeable misuse?
ISO 14971:2019 defines ‘reasonably foreseeable misuse’ as ‘use of a product or system in a way not intended by the manufacturer, but which can result from readily predictable human behaviour’.
Essentially, ‘reasonably foreseeable misuse’ refers to predictable use which is not included in your definition of intended use of the product. As you can see in the diagram above, there is a part of ’abnormal use’ which is out of scope because it is not foreseeable based on readily predictable human behaviour.
Performing risk management during medical device development
In performing risk management, it is important to remember to evaluate the adequacy and suitability of particular hazards, technical requirements and acceptance criteria throughout the entire process.
The risk management process will be used to identify essential performance. This analysis will include performance limits for relevant functions.
The ’expected service life’ of your medical device is defined as the time period during which you expect it to remain safe for use. This time period should be stated in the risk management file, although there is no specific requirement to justify it further.
The standard allows you to apply risk control measures and test methods, which are different to those defined by the standard. This can be particularly relevant in special cases which are not considered by the standard. In these instances, you must demonstrate that the residual risk is acceptable and comparable to that defined by the standard.
It is also important to assess the parts that can come into contact with the patient but do not meet the definition of an applied part. Your risk assessment determines if the part meets the requirements for a type B, BF or CF applied part – except from labelling.
Single fault conditions for medical devices
Let’s take a look at single fault conditions from a different perspective. Generally, devices should be designed and manufactured to remain single fault safe, at least if you cannot demonstrate that the risk remains acceptable in case of a fault.
With each design feature, you have two options to show that your device is single fault safe. The diagram below exemplifies this.
The first option is to design the feature in a way in which you can demonstrate that the probability of failure is insignificant. The diagram above includes examples of reinforced insulation, a mechanical tensile safety factor of 8 times and choosing components with high-integrity characteristics.
Your second option is to implement two independent risk control mechanisms. To qualify, you must justify either that the initial fault is detected before the second mechanism fails or that the probability of second fault is insignificant.
Both options should be applicable to the entire expected service life of the device. Your risk analysis should determine which single faults should be evaluated by test or simulation.
Power supply requirements for electrical medical devices
As all medical electrical equipment need an electrical supply of power, there are a few general requirements to the power supply and these are defined by Clause 4 of the general standard 60601-1. The power supply source can be supply mains, a special separate power source or an internal one, such as a battery.
The standard specifies a maximum rated mains voltage corresponding to the typically available AC mains. It also provides some general assumptions on the supply mains voltage. These are overvoltage category two, used to determine test levels for mains transient voltages. So, unless you specify otherwise, the requirements for category II apply.
You can assume the mains voltage is between 90 % and 110 % of nominal and practically sinusoidal. The mains frequency is below 1 kHz and the deviation is 1 Hz. Under these conditions, the steady state input power of the device shall not exceed markings by more than 10 %.
Many of these requirements are key to identifying specific requirements according to the later clauses in the standard.
Would you like to know more about safety for electrical devices?
If you want to know more about the 60601 standard and safety for electrical devices, take a look at our online course Introduction to Safety for Medical Devices and IEC 60601. This comprehensive course has in-depth information and quizzes to test your knowledge and understanding. At the end of the course you will also receive a course certificate, which many auditors will be looking for.
Our online courses are frequently taken by competent authorities, notified bodies and medical device manufacturers and distributors.
Claus Rømer Andersen
Claus Rømer Andersen is an accomplished trainer, consultant and facilitator in the medical device industry. With a background in electrical engineering, he has worked with regulatory navigation, approval management, device testing throughout his whole career.
He is recognized as having a pragmatic and solution oriented approach to helping development teams focus on relevant issues throughout the entire product life-cycle.