Usability studies medical devices

Usability in medical devices is a process that aims to design a medical device in such a way that it is easy and intuitive to use, the interface is tailored to the user and its use provides the highest possible level of effectiveness and safety.

Usability studies

Usability of medical devices, aims to ensure that medical devices are used correctly, reduce the risks of incorrect use or malfunction, and thereby increase their effectiveness.

What is a usability of medical devices?

Usability is a process that aims to design a medical device in such a way that it is easy and intuitive to use, the interface is tailored to the user and its use provides the highest possible level of effectiveness and safety. The principles of this process are regulated by IEC 62366, according to which usability engineering includes, among other things

• analysing the users who will use the product,
• the design of interfaces adapted to them,
• preparing clear instructions for use,
• development of different use scenarios,
• identification of potential errors resulting from inappropriate use,
• usability testing, in which different scenarios are tested in practice.

Usability engineering is closely linked to the risk assessment of the safe use of the medical device. The use of the device – including inappropriate use – must not be allowed to result in an unacceptable risk to the user. Guidelines for risk management are set out in ISO 14971.

Medical devices on the market must comply with the strict legal requirements set out in MDR 2017/745. The final product must be as safe as possible and has to provide convenience of use and certainty of results. This is important because a patient’s health or even life may depend on their performance. Ultimately, usability engineering and risk management are therefore intended to improve comfort, patient outcomes and quality of healthcare, ideally without side effects.

Medical device user analysis

When designing a medical device, we start by identifying who will use it. The needs, capabilities and expectations will be different for the medical staff in a specialist clinic, for the paramedic in an ambulance, and for the patient who will use the device independently at home. It is also important to determine under which conditions the device will be used.

Usually, this step is developed in the form of a questionnaire or form, answering questions about who will use the medical device, for what purpose and under what circumstances. This is the starting point for interface design.

Medical device prototypes and interface

Based on the information collected, prototypes of devices and their interfaces are designed. We usually associate the interface with a smartphone or computer screen, but in the case of medical devices it is a much broader concept. It encompasses not only the screen or buttons of the device, but holistically refers to the ability to interact with the device – the messages that appear on it, the audible signals that are given in certain situations, the touch panels or even the user manual.

Instruction for use

During the prototyping stage, an outline of the instruction for use is also prepared. This contains a description of the device, step-by-step rules for using it, and possibly installation or maintenance requirements. Usually, the Instruction for use also includes pictures to make the instructions easier to understand and to get to know. Basic safety messages should also be included.

Simple and unambiguous information makes it easier to learn how to use and reduces the risk of misuse or mistakes when using the device. Convenience and ease of use often translates into treatment outcomes as well.

For example, a device that measures glucose levels on its own and alerts the patient to exceedances with an appropriate message, compared to a traditional blood glucose meter that requires a needle, strips and precision, will significantly improve comfort and reduce response time – especially in emergency situations.

Usability tests

Prototypes equipped with instructions are then extensively tested by potential users in target-like conditions. This identifies problems and errors. Based on the analysis of comments from testers, the prototypes are modified and improved. Subsequent iterations are tested again, and the result is a product that is intuitive to use and potential errors resulting from misuse are reduced to a minimum.

During usability testing, the user manual is also evaluated and developed based on feedback from users. Users assess it in terms of readability and whether it helps with any difficulties encountered. At this stage, information about possible errors, their effects and how to avoid them and solve potential problems is usually included.

The final version of the manual should also contain all the elements required by legislation, including, technical specifications, compliance with standards and safety certificates, warranty conditions and service information.

Risk assessment

During the usability testing phase, risks related to the safe use of the medical device are also assessed. These include checking for the possibility of erroneous results when used correctly and errors resulting from unclear instructions, unintended actions or awkward handling. Great emphasis is also placed on previously unforeseen side-effects occurring. The next step is to modify the interface, functionality and instructions and develop strategies to reduce risks.

Usability for software as a medical device (SaMD)

In many cases, software itself can perform medical functions. Examples include mobile apps for monitoring heart rate or controlling blood sugar levels, software used in diagnostics – e.g. analysing medical images to identify a stroke, or software to help analyse blood samples and interpret the results.

Usability, in relation to software as a medical device, refers to how easily and safely users can use it under the intended conditions, with minimal risk of error.

Software as a medical device must therefore be:

• intuitive and easy to read to maximise user experience in different conditions, on different screens, by different users and in different situations – especially stressful situations,
• safe – the user’s interaction with the device should not pose a risk of serious consequences, e.g. misdiagnosis, delayed treatment,
• effective – the software should provide reliable data.

Here again, usability testing and real-world testing by the target users is essential. Here it is particularly important to minimise usage errors. Such errors can result from overly complex processes or not very intuitive navigation, but also from misunderstanding the results or taking the wrong action after receiving an alert.

The software should come with clear instructions for use and, if necessary, training materials to help users better understand how the application works. Technical support and updates should also be readily available to provide ongoing support to users.

Active medical devices – usability tests

Active medical devices are devices that need external power sources to operate and can be disrupted by various factors. The term usability for active medical devices, or stability, therefore, refers to the maintenance of functionality, safety and accuracy, despite the influence of external conditions such as temperature, humidity, vibration or operating time. Stability is the confirmation of a device’s ability to perform as intended over the long term, safely and efficiently.

What factors affect the stability of active medical devices

• Energy source – devices that depend on external energy sources must be designed to ensure stable operation under unstable or no power supply conditions, otherwise they can cause a risk to patient health and life
• Environmental conditions – medical devices are often used in harsh environments – varying temperatures, contact with moisture, disinfectants, or exposure to shocks and vibrations. They should therefore be made of materials that can withstand these conditions well.
• Natural wear and tear – many components will wear out during use, so care must be taken to ensure regular maintenance and servicing of the devices.
• Software – active medical devices usually use specialised software. Regular updates are therefore important.

Before being launched on the market, active medical devices are subjected to rigorous stability and environmental and mechanical tests over time, in addition to standard usability tests.

Usability of legacy devices

Legacy devices are MDD-compliant medical devices that were designed and implemented many years ago may not meet modern usability standards. Despite this, many such devices are still in use in hospitals and clinics, which poses challenges for their continued use:

• they are incompatible with modern devices,
• they are not ergonomic, and their operation is unintuitive,
• outdated interfaces, lack of clear messages and complex operating procedures can lead to user errors, affecting patient safety.

How can the usability of outdated medical devices be improved?

• Updating the software – refreshing interfaces, improving navigation and adding more intuitive options to facilitate communication with the device.
• Modifying the operating instructions and simplifying the processes leading up to the purpose
• Device upgrades – e.g. control panel replacement, touch screens

Usability testing and risk management in accordance with the MDR

Under the provisions of the MDR Regulation, the manufacturer of a medical device is required to ensure that the device is designed and manufactured to be safe and effective, which includes analysing and controlling the risks associated with the use of the device, including inadequacies associated with user error in the use of the device. Medical devices must also be appropriately labelled and contain instructions for use that can be understood by end-users to minimise the risk of errors due to misuse.

The requirements of the regulation are further clarified in standards:

• ISO 14971, which provides a framework and guidelines for identifying, assessing, monitoring and controlling risks associated with the design, manufacture and use of medical devices.

According to this standard, an error is a defect in a device or system that results in a malfunction of the device and may pose a risk to the patient.

An example would be an incorrect setting of the unit of measurement in the software of an insulin pump, so that the amounts of drug administered by the device are unknowingly too high or too low. This can endanger the health and life of the user.

• IEC 62366-1 focuses on usability engineering and therefore on potential errors on the part of the user.

It defines an error as an action that leads to a different result than was intended by the manufacturer or as the absence of a required action. In this case, the fault does not lie with the device or its software, but with the user. However, the cause may be unclear instructions or overly complicated operation. Such situations should be identified at the usability testing stage and eliminated before the product is launched on the market.

The final element is the summative evaluation, which confirms the safety of the medical device, and that the product meets expectations regarding its functionality in real-life conditions of use. At this stage, the testers are the people who will ultimately use the devices, the tests take place under real conditions, and they perform the tasks for which the devices are designed. An evaluation report confirming that the safety and usability requirements are met is necessary for the medical device to be placed on the market.