Intertech Engineering Associates, Inc.

The Essential Performance SNAFU part 3 of 4

As discussed in a previous part of this series, the family of the general standard IEC60601-1 includes collateral and particular standards that might apply to the manufacturer’s particular device. This part of the article series will highlight what collateral standards to IEC60601-1 have in them as well as what the particular standards address with regards to performance and essential performance of a medical device.


Examples of IEC60601-1 Collateral Standards

Collateral standards cover broad subjects, and for IEC60601-1 there are several. Below is a list of the current popular collaterals to IEC60601-1 and a brief description of what they cover:

These standards may apply to a manufacturer’s device and typically add additional requirements to the clauses of IEC60601-1 and include the testing and testing fixtures that would apply. When applying these standards, testing would require that the determined Essential Performance (EP) be evaluated during the test. After applying testing per the collateral standard there is an evaluation of the essential performance and a determination is made by the tester if EP is impacted to a point where harm can occur. Adding the Essential Performance to the test criteria was all new to certified test houses, used to evaluating only Basic Safety. Evaluation and monitoring of Essential Performance during and after testing requires a more advanced understanding of the device’s clinical impact to correctly conclude on the device’s safety. In reality, the acceptance criteria got a lot harder for testers and test houses to appropriately distinguish a passing device from a failing device.

The Essential Performance characteristics are the aspects we check for safety in standards tests; therefore there is a consequence if the EP items are not chosen correctly. If lower level, technical characteristics are identified as the Essential Performance characteristics, then we may incorrectly fail a device, where safety is not truly impacted.  If true Essential Performance characteristics go unidentified and are not addressed or tested to a point there is a potential for harm, then testing would be ineffective and the device may be released with safety inadequately addressed. This puts a lot of selecting what the Essential Performance characteristic is correct.

What Does System Engineering tell us about determining Performance measures?

Performance measurement from a system engineering perspective may include the consideration of measures of effectiveness and measures of suitability. Measures of effectiveness are measures that correspond to the accomplishment of mission objectives and achievement of the desired results. These performance measures are determined through a capabilities-based assessment of the system and its objectives. Examples of these performance measures include the characteristic of measure of a system’s performance expressed as a speed, payload, range, time-on-station, frequency, or other distinctly quantifiable performance feature. Performance measures considering suitability include a performance measure of an item’s ability to be supported in its intended operational environment. Examples of these performance characteristics typically relate to readiness or operational availability, reliability, maintainability, or the item’s support structure.

The above characteristics of performance are different from technical performance measurements. Technical Performance Measurement (TPM) involves a technique of predicting the future value of a key technical performance parameter of the higher-level end product under development based on current assessments of products lower in the system structure (per EIA-632 “Process for Engineering a System”) 1.

Manufacturers defining there performance characteristics need to determine which performance measures that correspond to mission objectives and suitability when defining Essential Performance and not fall into the trap of cycling through all technical performance measurements made on a device to determine what the essential performance is.

Particular (dash 2 Performance) Standards

As mentioned earlier, Particular standards include a list of Essential Performance characteristics in the standard. Looking at some particular standards for IEC60601-1 will help us understand what these performance characteristics look like. The Essential Performance characteristic may include areas such as the accuracy with which the equipment controls the delivery of energy or therapeutic treatment to the patient, as well as the devices ability to process and display physiological data that will affect patient care decision management.

The IEC60601-1 Particular Standards are available for some specific medical devices. These standards are represented by the IEC 60601-2-xx series, and are often referred to as “dash 2 standards.” Some examples of particular standards for IEC60601-1 are provided below. For those devices that do not have a dash 2 standards, the determination of Essential Performance is left to the manufacturer as defined in IEC60601-.


Examples of Essential Performance Characteristics from the Particular Standards

In addition to providing the Essential Performance characteristics for a medical device, the particular (dash 2) standards also include additional clauses that would replace or delete requirements that are called out in the general standard (IEC60601-1). The below table provides an example of some of the Essential Performance characteristics identified in a sampling of particular standards.

Table 1: Examples of EP items for some medical devices.

The definition of Essential Performance is defined per IEC60601-1 section 3.27 as:

“performance of a clinical function, other than that related to Basic Safety, where loss or degradation beyond the limits specified by the manufacturer results in an unacceptable Risk.

Note Essential Performance is most easily understood by considering whether its absence or degradation would result in an unacceptable Risk.”

In the review of table 1 above, it is clear that the actual acceptable performance levels are not prescribed, but left to the manufacturer. Additionally, the approach for how the characteristics are to be described across a sample of particular standards is not necessarily consistent. In some cases, the clinical function of the essential performance characteristic is not part of the specified item, as in “Alarm signals for high priority alarms” for infusion pumps. But, the consideration for what the actual acceptable performance level is as well as how these essential performance characteristics are to be applied while evaluating or testing the device is left to the discretion of the manufacturer. The note in the definition of 3.27 above does provide for how manufacturers should determine the specifics as well as what the acceptable performance ranges are. Once performance degrades to a degree that the risk is unacceptable (and harm can occur), this is when an unsafe condition or state has occurred (and therefore operating out of the determined range is unacceptable).

FDA Recognized Consensus Standards

The FDA recognizes standards that are deemed appropriate for manufacturers of medical devices to declare conformance with. The table above shows which of the example particular standards are FDA recognized consensus standards. The use of consensus standards to meet premarket submission requirements can help the FDA premarket review process although this is ultimately up to the submitter. Although the FDA reviewer may request the submitter to comply with a particular standard, as well as submit test data, as is the case with ISO 10933-1 for the Biological evaluation of medical devices. Additionally, if the standard is not FDA recognized, it doesn’t mean a reference to it or compliance to will not be considered acceptable by the FDA. The submitter can determine which standards the FDA suggests or recognizes by accessing the FDA website of recognized consensus standards, or determining if an FDA guidance is applicable that may also identify applicable standards.

From clearance standpoint, the FDA may not be as focused on identifying Essential Performance or testing Essential Performance, but they will be looking for the manufacturer demonstrate safety. The FDA has moved over the years to rely on standards, as well as identifying standards they recognize, but they always reserve the right to require more, regardless of what some of the IEC standards may require. In some cases, the FDA will put out FDA guidance documents that provide expectations on manufacturers for how performance is to be indicated and tested. The FDA has also indicated that risk can be used to determine what areas of a medical device require attention, but they have yet to say they are only interested in attending to only Essential Performance characteristics.

The next part of this article series will provide some examples of what has happened to the industry when Essential Performance is not correctly identified, as well as provide some recommendations for manufacturers. We are interested in your experience with Essential Performance and hope you will contact us and share them with us.

1 –“Processes%20for%20Engineering%20a%20System”%207%20Jan%2099.pdf

Understanding Cybersecurity Risk

Date: 1 25 2018    By Geoff Hutchins, Harold Pogue, Mohammad Raza

Understanding Cybersecurity Risk

Like other risk management perspectives, business and product, addressing cybersecurity needs to be considered throughout the development process[1].

A key part of this is understanding the types and classification of the cybersecurity risk[2] as a framework for assessment and development of control measures.

There are several viewpoints that should be considered when setting this up as follows:

  • Classification of the nature of the risk, malware, riskware, spyware etc.
  • Product lifecycle stage, premarket, post-market and legacy device
  • Risk introduced using OTS & SOUP libraries[3]
  • Product intended use, use environment, and hazard profile, life-sustaining, diagnostic, hospital or home
  • Classification by core functions, Identify, Protect, Detect, Respond and Recover
  • Classification by means of access, network connected, wirelessly, USB and medium such as CD

There are several existing frameworks that a manufacturer may consider using:

  • NIST Cybersecurity [4]
  • Common Vulnerability Scoring System (CVSS)4
  • AAMI TIR57 Principles for medical device security – Risk Management
  • UL 2900 Testability of network connected devices.

Cybersecurity Risk Management Process

The cyber risk management should be considered as part of the product lifecycle management:

  • Conduct product requirements cyber risk analysis and assessments.
  • Evaluate code, library and tool vulnerabilities and validations.
  • Plan and execute penetration testing on product configurations.
  • Document testing and re-evaluation plans for new threats
  • Plan for the deployment of updates and associated cybersecurity risks deploy cyber risk.

Some essential ways to mitigate risk include the following:

  • Require the user to update the default password of the device. Default passwords, especially for networked devices, are well known and can be exploited. Use longer passwords with a strong measurement of randomness.
  • When designing the device avoid using WEB/PSK/TKIP. These are no longer considered secure and have been depreciated. They share the same key and if that key is compromised, all devices in the network that communicates with that key are vulnerable.
  • Ensure that all data at rest is encrypted. It is also good practice to create backups prior to any change and to ensure the device user on how to recover the backup. If data is stolen the encryption should maintain privacy.
  • For software as a medical device, it is necessary to designate a patch management facility/process. Patches are common but can sometimes cause problems. Having a process in place that verifies that the patch works on the equipment before wide-scale deployment will minimize risk.
  • Have a periodic device verification plan and perform regular audits.
  • Perform security tests and provide these to the end user. These tests should include encryption, authentication, patches to the software, and version of virus protection.

[1] Content of Premarket Submissions for Management of Cybersecurity in Medical Devices, Guidance for Industry and Food and Drug Administration Staff, October 2, 2014

[2] IEC TR 80001-2-2 Edition 1.0 2012-07 Application of risk management for IT Networks incorporating medical devices.

[3] Guidance for Industry, Cybersecurity for Networked Medical Devices Containing Off-the-Shelf (OTS) Software, January 14, 2005.

[4] Postmarket Management of Cybersecurity in Medical Devices – Final Guidance, FDA presentation January 12, 2017, CDRH Webinar


Medical Device Validation Series 3 of 4: It all Starts with Requirements

Part 3, It All Starts with Requirements

This is part three of a four-part series on medical device validation practices.

Is writing requirements a validation activity? Of course, it is! What has been verified if verification testing is attempted without written requirements? The GPSV points out: “Success in accurately and completely documenting software requirements is a crucial factor in successful validation of the resulting software.”

There is some room for debate on what constitutes a requirement and what constitutes design detail. While much benefit derives from solid, well reviewed requirements that have nothing to do with testing, the testing effort should be based on verifying the correct implementation of requirements.

Tests should test requirements. Too often, tests are written without detailed requirements or not enough detail in requirements (exploratory testing), and the test developer is forced to refer to the software for details regarding how the software works. The result is that the test ends up documenting the way the software works, not necessarily the way it is supposed to work. The requirements for the software are embedded in the test, not in a requirements document. Many problems are associated with this, but perhaps most alarming is that potential problems can get embedded into tests as expected behavior—thus, making it difficult to identify them as problems, and guaranteeing that the behavior will be accepted forever after.

From: Vogel, David A., Ph.D. “Validating Medical Device Software Includes and Goes Beyond Testing.” Medical Product Outsourcing Mar. 2006: .

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.



Medical Device Validation Series. Part 2 of 4

Part 2, Validation: More Than Testing

This is part two of a four-part series on medical device validation practices.

A common misperception is that validation of software is synonymous with the testing of software. This is not at all accurate.

Federal regulation requires software validation, not software testing. Validation, by the FDA’s definition, is the “confirmation by examination and provision of objective evidence that software specifications conform to user needs and intended uses, and that the particular requirements implemented through software can be consistently fulfilled.”

Certainly, testing activity may be a component of validation, but note that the definition above does not use the word “test” at all. In fact, the definition mentions specifications and requirements specifically, assuming they exist and therefore creates a de facto linkage between validation and requirements.

The GPSV describes at length the definitions of, and differences between, software validation and software verification. Only a few of the related activities would be considered test activities. Similarly, verification activities, though narrower in scope, involve reviews, evaluations, and testing activities.

Keep in mind that all verification and test activities are validation activities, with other activities making up the remainder. Some testing is considered a verification activity, but there are verification activities that are not testing activities, and there is also testing that is not verification testing. Stay mindful that validation is not the same as testing.,

From: Vogel, David A., Ph.D. “Validating Medical Device Software Includes and Goes Beyond Testing.” Medical Product Outsourcing Mar. 2006: .