Here’s a scenario.
You’re at the point of sending your new electrical medical device off for IEC 60601 electrical safety testing, and you anticipate the test lab asking if your medical device is considered Medical Electrical (ME) Equipment or a Medical Electrical (ME) System.
To provide an accurate response to the testing lab, you need to have answers to these questions:
What characteristics of my device would prompt the lab to ask whether it is categorized as an ME Equipment or an ME System?
What is the difference between the requirements for ME Equipment and ME Systems?
If you find yourself scrambling through IEC 60601 to answer those questions, don’t fret. This blog aims to help you understand a nuance in the standard that allows the manufacturer to determine the category of ME Equipment or ME System: external power supplies.
But first, let’s start with a summary of requirements, where IEC 60601-1 clarifies if the device is an ME Equipment or an ME System.
Compliance Engineer I
ME Equipment is typically internally powered, contains a single enclosure, or operates without connecting to different pieces of equipment. It may have accessories or detachable components required to achieve its intended use, and an internal or external power supply defined as an accessory. Think of it as a single piece of equipment such as a personal blood pressure monitor, fitness tracker, or glucometer.
ME Equipment cannot have multiple connections to a supply mains. That means anything that includes or is intended to connect to a multiple socket outlet (power strip) or receives power from two different supply mains (either directly or indirectly through other equipment) must be considered an ME System.
An ME System is a combination of numerous pieces of equipment, at least one of which is classified as ME Equipment interconnected by a functional connection or by use of a multiple socket outlet. Manufacturers need to keep in mind that functional connections include electrical connections and may include other connections, such as mechanical, optical, or wireless.
ME Systems can contain two different types of equipment, ranging from simple single-enclosure devices with an external power supply to complex imaging systems with medical and IT equipment. The combination of the equipment within the system must be specified by the manufacturer.
The only situation where the manufacturer has to define if the device is considered one piece of ME Equipment is when the ME Equipment connects to a separate power source other than supply mains, such as an external AC/DC power supply. This power source can be considered part of the ME Equipment, or the combination of the ME Equipment and external power supply can be considered an ME System.
Hopefully, we have already saved you at least 30 minutes reading through the standard.
Now, let’s walk through the concepts of different means of protection and the patient environment to understand how to intelligently define a device as ME Equipment or an ME System, reducing the chance of unnecessary non-conformances during electrical safety testing.
During an IEC 60601 engineering evaluation, an insulation diagram will be developed to indicate where the means of patient protection (MOPP) or the means of operator protection (MOOP) are required to be verified. The standard assumes a patient cannot respond to stimuli (such as heat or shock). Therefore, the means of patient protection require a higher level of safety than the means of operator protection.
ME Systems are required to maintain the level of safety equivalent to ME Equipment defined in the IEC 60601 standards for parts of the ME System within the patient environment or where it is likely the operator may come into contact with the equipment and the patient at the same time.
The patient environment is any volume of space where intentional or unintentional contact can occur between the patient and parts of the ME Equipment or ME System or between the patient and another person touching parts of the ME Equipment or ME System.
However, outside the patient environment, where only an operator may come into contact with parts of the ME Equipment or ME System, the equipment is only required to maintain the level of safety equivalent to equipment complying with their respective IEC or ISO safety standards such as IEC 62368-1 for IT equipment, such as a computer, since the level of safety provided by these standards generally match the level of protection required for MOOP in IEC 60601-1.
Although not specifically stated in the standard, the patient environment should be determined through the risk management process. The standard recommends a volume greater than or equal to 1.5 meters surrounding the patient, an acceptable patient environment volume.
IEC 60601-1 acknowledges it is difficult to define exact dimensions for the patient volume, however, the dimensions shown below have been justified in practice.
Common configurations of ME Systems and their relation to the patient environment are provided in Annex I of IEC 60601-1. A small sample of common configurations is shown below.
Incorrect labeling (yes, that includes the instructions for use) is one of the top reasons for failing electrical safety testing. There are additional labeling requirements for ME Systems that do not apply to ME Equipment. Knowing if your device is an ME Equipment or a ME System will help ensure compliance with labeling requirements.
It’s also important for manufacturers to understand the differences between MOPP/MOOP. Knowing when either one will be required (i.e., in or out of the patient environment) before implementing the design and selecting off-the-shelf components (such as power supplies) for any ME Equipment or ME System is essential. For example, the decision to make an enclosure 0.5 mm thicker in certain areas can make a difference in compliance with MOPP, and no one likes to go back and update a mold once it is believed to be finalized.
Knowing where MOPP and MOOP will be needed within the final ME Equipment or ME System will always help ensure a more direct path to market and reduce the chances of redesign required to comply with IEC 60601. It also allows a company to save on costs by choosing components needed to meet the safety requirements while still achieving the performance requirements.
Now, let’s look at an example in the professional healthcare environment where a manufacturer could have saved on some cost by choosing the “right” power supply for their device.
Consider a portable ECG monitor intended for the professional healthcare environment that runs on an internal battery and is charged using an external AC/DC power supply that plugs into the supply mains.
The device includes an internal mechanical means to prevent it from performing its intended use while connected to the external AC/DC power supply.
Would this external power supply be considered a detachable component of the ME Equipment, or does the combination of the portable ECG monitor and the power supply make up an ME system?
There are two potential paths:
The manufacturer includes a power supply compliant with IEC 60601-1 for charging the ECG monitor and classifies the combination as one piece of ME Equipment.
The manufacturer includes or specifies a power supply compliant with IEC 62368-1 and classifies the combination as an ME System.
Most IEC 60601-1 compliant power supplies provide the higher MOPP required by the standard and are, therefore, more expensive than IEC 62368-1 compliant power supplies. This additional protection and cost offer no benefit in this scenario since the power supply for the ECG monitor is intended to be handled solely by an operator, and the supply mains connection will be outside of the patient environment.
Defining the patient environment becomes more complicated in home healthcare when the patient also acts as the operator. Keep an eye out for future Criterion blogs where we discuss the nuances of the home healthcare environment as defined in IEC 60601-1-11.
See the table below for a summary of when an external “Medical” (IEC 60601 compliant) or “Standard” (IEC 62368-1 or equivalent) could be considered part of the ME Equipment or ME System.
Well, here we are.
That was a long journey, only to find out that it doesn’t really make a difference to the end result of an engineering evaluation whether or not the combination of the device and external power supply is considered ME Equipment or an ME System.
Regardless of the classification, as long as a part of the Equipment or System is within the patient environment during use, it is required to provide the necessary level of patient protection, which is particularly important with supply mains.
The main takeaway is that manufacturers can help save on re-design, raw material, and compliance testing costs by having a grasp on where the necessary means of patient and operator protection are required by the standards before making initial design decisions.
At Criterion, we’re committed to helping manufacturers navigate and understand the regulatory compliance testing pathway, and we’re here to guide and assist at any step of your journey. Don’t hesitate to reach out to us with any questions about the concepts in this blog or compliance testing in general by sending us a message at criterion@biotexmedical.com .
Nathan is a Compliance Engineer at Criterion, the testing services lab within Biotex. He played a leading role in achieving and maintaining Criterion’s ISO 17025 and ASCA accreditations. He has been with Biotex for over five years, focusing on regulatory compliance and medical device testing for three years. His primary goal is to ensure clients understand the regulatory testing requirements so they can make informed design decisions for a smoother path to market.
