Intertech Engineering Associates, Inc.

The Essential Performance SNAFU part 2 of 4

The Essential Performance SNAFU:

Defining what Essential Performance is for a medical device is a challenge, but the definition is especially challenging and often confusing when software is part of the product. This article series is intended to share what is happening in the industry once Essential Performance is defined, and provide some guidance on how to address compliance and safety avoiding the SNAFU’s we have observed in this process.


The compliance community has been using the Essential Performance (EP) to focus testing and evaluation of medical products since the 3rd edition of IEC60601-1 (published in 2005). Some medical device manufacturers are fortunate enough to have their Essential Performance defined for them through Particular standards if they are available for their medical device. Those less fortunate, who are left to define this for their products, are often challenged to determine what is essential.  This can often be confusing and we have found that industry test houses are not helping manufacturers make sound decisions when it comes to devices containing software.  


Part 2. Defining Essential Performance

The 3rd Edition of IEC60601-1 and Programmable Electrical Medical Systems (PEMS)

The changes made in the third edition of IEC60601-1 define a general approach of adopting two new main principles as described in the standards’ introduction. The first principle is the change in approach in the series of standards related to the concept of safety which has been broadened to include Basic Safety considerations and now Essential Performance matters. The second change in principle is the addition of a provision for assessing the adequacy of the process compliance when this is the only practical method of assessing the safety of certain technologies. There are two such examples that stand out in the standard, one being the application of ISO14971 risk management processes and the other is adopting software lifecycle processes to support programmable electronic medical systems (PEMS).  This PEMS consideration is clause 14 of the standard and it, when applicable, requires a software development lifecycle and software validation.  In considering these processes it is important to recognize that the ISO14971 standard requires a risk management process to support and assure safety and not just identification of characteristics of essential performance and basic safety per the IEC60601-1 standard. This article will further examine the consequences of how what is determined as essential performance might impact other supporting process standards.


Essential Performance (EP) and the Impact on PEMS

Examining the PEMS clauses further and clause 14.1 of  IEC60601-1 we find:

“The requirements in 14.2 to 14.12 (inclusive) shall apply to PEMS unless:

– none of the Programmable Electronic Sub-System (PESS) provides functionality necessary for Basic Safety or Essential Performance; or

– the application of Risk Management as described in 4.2 demonstrates that the failure of any PESS does not lead to an unacceptable Risk.”


Clause 14.1 indicates that PEMS applies if software provides functionality necessary for Basic Safety and Essential Performance or if application of clause 4.2 (ISO14971) does not lead to an unacceptable risk. An important part of note is the “or” part of the clause which might be easily ignored or missed when determining if the PEMS clauses apply. The PEMS clauses include the requirement to apply a software development lifecycle including software validation. The annex A in IEC60601-1 of the standard is intended to provide general guidance. In the annex A of the standard the guidance for clause 14.1 says this:


“Requirements have been minimized to those that are essential to assuring Basic Safety and Essential Performance. This has been done in recognition of the extensive and growing literature in the fields of software assurance and Risk Assessment techniques as well as the rapid evolution of this discipline.”


Is this suggesting that clause 14 (PEMS) is only applicable to Basic Safety and Essential Performance? There has been some indication that some manufacturers are interpreting that this is the case, and doing so with or without completing risk analysis on PEMS.


Interpretation of PEMS and Software Validation Driven by EP definition

There have been instances where clause 14 (PEMS) of the IEC60601-1 standard has been interpreted by medical device manufacturers that a software development lifecycle and software validation is not be required. The tendency of a manufacturer to conclude excluding additional, non-required processes and the additional resource costs and time needed for these activities is easy to understand. Unfortunately, manufacturers are already constrained by time boxed commitments, limited and dwindling budgets by the time they start looking at standard compliance. Additionally, many test houses are also concluding and complicit with manufacturers stating that if the software on a medical device can’t affect Basic Safety or Essential Performance then PEMS will not apply.  This has led to cases inside and outside the US,   where manufacturers have excluded implementing a software development lifecycle and software validations, to find out later the consequences of this.


Is a Software Development Lifecycle and Software Validation Important?

It is easy to agree to the premise that software validation for a medical device, where the safety of the patient is at risk, should be performed by the medical device manufacturer to provide adequate assurance the software in a device is safe. But is following a standard and applying software development activities and validation always a good idea?


Advances in technology has gotten us to the point where software has become a more and more significant driving force in how all devices with hardware operate. There is literature as well as our personal experience to support that the practices of defining objectives, agreeing on requirements, planning tasks and activities and analysis and testing of potential solutions lead to a higher confidence in outputs that meet intended needs. With this in mind, we would not recommend complete exclusion of the application of a software development lifecycle and development process nor some level of software validation on any product, whether it be a medical device or not.  Even companies that provide consumer products apply some software development process and testing; does it make sense that complete exclusion for a medical device is sensible?


Is the Process for Identifying EP the Same as Conducting Risk Analysis?

ISO14971, the Industry recognized standard for risk management has been around since 2000. This standard requires systematic use of available information to identify hazards and to estimate the risk for medical devices. Typically, risk analysis is conducted by identifying hazards including the use of an examination of potential systematic failures, such that the risks associated with the device can be evaluated. Examining systematic failures requires a bottom up analysis, where the known and previously unknown hazards and potential harms are evaluated and discovered.


Basic Safety refers to physical hazards; this is defined in clause 3.10 of the 60601-1 standard and was discussed in the previous section of this article. The identification of the Essential Performance aspects can be limited to those aspects that fall under what is performance as well as what is a clinical function as per section 3.27 of IEC60601-1. Do the definitions of Basic Safety and Essential Performance together include consideration of all potential Hazards? Examples of Hazards provided in Annex E of 14971 include evaluating functional operational failures for risk, providing examples such as “Incorrect or inappropriate output or functionality” or “Erroneous data transfer”.  What makes this challenging for manufacturers is whether a hazard such as these examples is something that is evaluated (or identified) by following IEC60601-1, particularly if these failures don’t fall under the definition of Essential Performance or Basic Safety. In some cases manufacturers are limiting the identification of risk controls if the function or characteristic is not defined as Essential Performance or Basic Safety and may not be supporting these conclusions through the process of risk management to assure their product is safe.


Is the FDA Using EP and is it the same as “essential to the proper functioning of the device”?

The FDA Design Controls refers to a process of identifying characteristics that are essential for the proper function of a medical device. This design control regulation and guidance was written and in place before the IEC60601-1 standard defined Essential Performance. The FDA Design Control Regulation was put in place in 1996 and identified in section 21 CFR 820.30(d) that:


“Design output procedures shall contain or make reference to acceptance criteria and shall ensure that those design outputs that are essential for the proper functioning of the device are identified.”


The obvious conclusion is that both Essential Performance of a clinical function and identifying what is essential to the proper functioning of the device should both be outputs of risk analysis, although this may be a result of risk analysis focused at different points of the hierarchy of the system. For example, the evaluation of risks related to clinical functionality is closer to the inputs and at the top of the system architecture versus evaluation of risks of device system or software functionality which are closer to the outputs and at a lower level of the design.


The FDA clears medical products through the premarket notification process, much like a notified body provides medical product manufacturers a CE mark. The FDA provides guidance for what the manufacturer should submit. For medical devices marketed in the US the regulation requires medical device software validation and risk analysis per 21 CFR 820.30(g). The FDA regulation is less prescriptive in terms of what the process is for risk analysis. The FDA Guidance for the Content of Premarket Submissions for Software Contained in Medical Devices, issued in 2005, is more prescriptive on what documents are submitted for the medical device submissions. This guidance requires submissions to contain some level of documentation for hazard analysis and software validation for ALL medical devices that contain software, for all levels of concern.  The FDA General Principles of Software Validation, issued in 2002, defines what is expected for software validation.


The FDA General Principles of Software Validation does provide a provision for the scale of the software validation effort in that they say that:


“The resultant software validation process should be commensurate with the safety risk associated with the system, device, or process.”


This statement in the FDA guidance is similar to what IEC60601-1 is getting at with identifying Essential Performance characteristics.  They are both derived through an evaluation of risk, although the Essential Performance characteristics are limited to the “performance of a clinical function” per its definition. The interpretation that risk analysis and applying a software development lifecycle, including software validation is obviously not something the FDA expects manufactures to exclude in their processes, or in submissions for clearance to market.


The FDA’s expectations of voluntary standards and performance standards will be further discussed in the next section of this article series.  We would be interested in your own experiences with essential performance and if you have had issues with CE marking process or the FDA.



Leave a Reply

Your email address will not be published. Required fields are marked *