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Ergonomically Sound

Medical devices are used by a multiplicity of users and in a variety of environments. Manufacturers of these devices will therefore need to be aware of differences in skills, needs, abilities and preferences among users, as well as the requirements that pertain to different contexts of use, whether they are in the hospital or the home.

It is well established that medical devices should be designed to fulfil the requirements of the user. Recent research has demonstrated the clear links between the design of medical devices, poor usability, human error and patient safety. As a result of this, it is now a legal requirement for medical device manufacturers to address the usability of their products before they can be placed on the US and European markets. Manufacturers have to provide evidence, through compliance with standards such as ISO/IEC 62366 and HE75 that they have applied ‘human factors engineering’ (also known as user-centred design (UCD), ergonomics or usability engineering) throughout development.

However, as well as improving safety, a user-centred approach to development can have many additional benefits, such as improved effectiveness, ease of use and learning or training, fulfilling hygiene requirements and addressing maintenance, servicing, storage and labelling. In addition, attention to factors such as comfort, aesthetics and portability will improve the patient experience and may improve adherence to treatment regimes. In this article we discuss the crucial role of the end-user in the medical device product pathway, and describe how to conduct practical yet meaningful user research at each stage of development.

A User-Centred Approach

UCD is an ergonomics approach that focuses on users, their capabilities and needs throughout planning, design and evaluation. It is recommended that UCD should begin at the earliest stage possible, ideally at concept, and continue through an iterative design and evaluation process (see Figure 1). A UCD approach will involve a variety of research methods dependent upon the stage of product development and the data required.

An error often made by manufacturers is not to consider users sufficiently in the early stages of development and decide to wait until they have a prototype. However, this can lead to manufacturers making inaccurate assumptions about who the device users will be, how they behave, and what they want.These assumptions may soon become accepted, and if these are incorrect or incomplete, then the device will be developed and evaluated based on incorrect information.This can have serious implications, not just for the safety of the new device, but also for its commercial success.

Stages of User Research

Figure 2 shows an illustrative medical device product pathway and shows how user testing can map onto each stage of development. Broadly speaking, the aims of the first two stages are to identify the requirements, and the aims of the second two stages are to ensure that the device meets those requirements.

Stage 1: Identify a Need for a New or Improved Device
The aim of early user research should be to establish whether a new device is necessary.There are many possible Ergonomically Sound Medical devices are used by a multiplicity of users and in a variety of environments. Manufacturers of these devices will therefore need to be aware of differences in skills, needs, abilities and preferences among users, as well as the requirements that pertain to different contexts of use, whether they are in the hospital or the home. reasons for developing a new device, such as: improved patient outcomes; making a task quicker, easier or more cost-effective; improved service quality; and improved safety.

At this stage in the process,we are unlikely to know what all of the relevant issues are, and so it is important to keep the scope of the research as broad as possible so that all possible clinical needs are identified.When talking to users they should be encouraged to talk widely and in detail about the things that make their life or work difficult, unpleasant or unsafe.The aim should be to fully understand what it is like to be that user: what it is like to nurse patients with end stage lung cancer for example, or to live with a chronic condition such as cystic fibrosis.

If some information is already known about the potential device then a more focused study may be appropriate. For example, a surgeon may have reported a problem with a particular procedure and identified a need for a device to solve it. In such a case, a detailed study of the procedure would be required using a method such as task analysis, ideally in a number of hospitals and with a number of surgeons to understand how and why the procedure varies.

The goal at this stage is that the manufacturer will have a clear idea of the clinical benefit of the new device as related to its user(s).

Stage 2: Validate and Refine the Device Concept
Once an initial concept or need for a device has been identified then a more detailed user research study should be conducted. At this point the aim should be to fully understand the potential users of the device; the environments in which the device will be used; and the tasks that it will be used to perform. When considering who the users are, this should include not only the ‘target users’ that the device is actively designed for, but also any other individuals who may happen to use the device.

The focus at this stage should be the attributes, capabilities and requirements of the potential users. For any one device there may be multiple user groups and within each group there will be substantial variation due to factors such as ethnicity, educational background, socio-economic group or physical characteristics.The focus should be on identifying and understanding the issues relevant to the particular device. For an assistive device this would be the physical capabilities of patient users (and perhaps also their carers), the everyday tasks they perform, and the environments in which these are done. For an infusion pump, the focus would be more towards the skills and working patterns of clinical users.This information will be needed for the design of the device, but it will also be required to identify training needs.

Specifying the use environments and clinical tasks is an essential part of meeting medical device usability standards. Manufacturers are require to identify the situations that will constitute ‘normal use’ and ‘correct use’ of their device, and also identify any potential hazardous situations associated with this type of use.When considering how their device will be used, manufacturers should recognise that users will regularly adapt the way they operate devices.This may be to save time or it may be because of a clinical emergency. What constitutes and can be defined as ‘normal use’ and the risks associated with this are important issues when seeking regulatory approval for a medical device and must be documented for compliance with ISO/IEC 62366.

By the end of this stage, the manufacturer will have identified the user-related information necessary to produce one or more prototype designs: the user requirements document. Once the critical user issues have been identified this will allow the developers to decide on the measures to use during the evaluation stage. Examples of such measures include:

  • Programming the device must take no more than 90 seconds
  • The device will need to be user-friendly for a wide range of users, including those with no professional training
  • The device must be compatible with devices x and y, where x and y are predetermined and could be accessory devices
  • The device must be usable by people with severe arthritis

Stage 3: Design
At this stage, some difficult design decisions have to be made. For many devices the users will include a wide variety of people, potentially including both professionals and lay users and with differing specialities, skills and abilities. Once the requirements of all of these have been identified then any conflicts will have to be resolved.This will require decisions to be made on whose needs should be prioritised.This may be the primary users or those users who may be more vulnerable to making errors.This stage should ultimately provide a testable prototype.

Stage 4: Evaluation
A fundamental principle of user-centred design is that evaluation should be iterative and involve a number of cycles of evaluation, re-design and further evaluation.

Evaluation of a prototype device will not only involve safety and usability issues, but also other critical factors such as functionality, clinical efficacy and cost viability. It may be tempting to delay user testing until a high-quality, fully functional prototype has been developed.However, leaving user evaluation until late in the development process can be problematic. For example, if a device has already been CE marked or met other regulations, then changing seemingly small issues, such as the shape of a device or moving buttons on the user interface, will require re-certification and therefore may become too expensive or time-consuming to implement.

User evaluation, therefore, should be conducted alongside the functional evaluation of a product so that changes based on user feedback can be made at the same time.This will normally mean that early evaluations will be performed outside of the clinical environment.

Evaluation criteria against which the device will be tested should be based on the user requirements document that was developed in stages 1 and 2. Examples of criteria for success include:

  • The new device will reduce task errors by 60 per cent, thereby improving patient safety
  • 90 per cent of users will be able to use the device safely without training
  • The new device effectively supports the working practice of the users by providing constant feedback on infusion status
  • The device can be used in predetermined settings without additional support

As well as safety, success criteria will also include clinical, functional, organisational and economic aspects:

  • Using the device will allow procedure x to be performed an average of 15 minutes quicker than current practice 
  • The new device enables patients to live more independently by providing them with an effective method of treating themselves

In the early stages of evaluation, the likely outcome will be the identification of a number of issues that will require changes and improvements to be made to the device, for example:

  • The screen must be brighter as it cannot be viewed in low light conditions
  • The device should also display blood pressure
  • Clearer and more detailed instructions are required
  • The alarm tone should be changed if it is too similar to that of other devices in the clinic
  • Audible feedback should be provided to the user when buttons are pressed

It is important to set the goals of evaluation before commencing so that the performance of the device can be measured objectively.Detailed and rigorous early user research will answer whether the device meets the needs of its users.

As with all stages of device development, there is unlikely to be complete agreement between users as to whether their requirements are being met and therefore some requirements may have to be sacrificed in order to prioritise issues, such as patient safety.

Presenting the Results

Medical device usability standards require that the methods used during device testing are made available to purchasers and users. For instance, if testing has been carried out in a simulated clinical environment, it is important that purchasers are made aware of this and the restrictions to the validity of the testing that this may entail. Similarly, if testing has not included the possible use of the device by untrained staff, then this may affect the controls that are put on use of the product by such users, since the errors they could make will not have been accounted for.The American standard AAMI/ANSI HE75 (Human factors design process for medical devices) provides guidance on the sort of documentation that should be produced.

Research Methods

The choice of methods to be used at each stage of development will depend on a number of issues including the types of users to be studied and whether the aim is to understand user behaviour or their thoughts and feelings.Method choice will also be influenced by whether we are interested in capturing the views of individuals or the views of a group. For example, the interaction in a focus group discussion can result in a large number of opinions and experiences as participants bounce ideas off each other. However, in a group situation an individual may find it difficult to express an opinion that will conflict with the rest of the group or to raise personal or sensitive topics. In addition, it can be difficult to manage groups of individuals from different social, cultural or professional backgrounds.

Manufacturers should not rely solely on discursive methods as these are only able to collect information that users are willing and able to articulate at that particular moment in time. A discursive method should ideally be complemented by performing a task analysis or some type of observational study of the task or environment in order to understand the context of use or the behaviour of users. Contextual inquiry is an effective method for identifying information about dangerous or inefficient practice that users may have become so familiar with that they aren’t consciously aware of them. Ideally,more than one method should be applied at each stage of development to gather different types of data. For example, an observational technique such as contextual inquiry may identify a number of issues which can then be investigated further with interviews or a focus group.

Remember to Challenge your Assumptions!

An important function of user research is to challenge the assumptions of the development team. It is tempting to convince yourself that there will be a huge market for your new device and that it is going to transform the healthcare industry, especially if you are closely involved with a project. This can lead to the so-called ‘ugly baby syndrome’, where developers ignore dissenting opinions or negative information about their product. This is entirely normal; well established cognitive biases mean that we are predisposed to search for and interpret information that confirms our beliefs and place less importance on or ignore any information that contradicts it. It is also important to remember that it is impossible to put yourself in the shoes of the person seeing and using your device for the first time when you have spent many months or years working with a device.


Performed at an early stage, UCD need not be an onerous task and will contribute to a product that is demonstrably fit for purpose. Selection of appropriate methods at the start and at subsequent stages of the device development process is critical to efficient use of resources in performing UCD. Some of these methods have been described here. Now that regulations and new standards are in place, UCD for medical devices will no doubt mature in years to come and will be considered no less routine than any other vital aspect of the development process.

Further Reading
NPSA Design for patient safety: user testing in the development of medical devices,

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Michael P Craven, Senior Research Fellow at the University of Nottingham and member of the UK wide Multidisciplinary Assessment of Technology Centre for Healthcare, is engaged with applied projects in collaboration with MATCH’s industry and health service partners, primarily in the area of medical device evaluation methodologies and tools. Michael obtained his PhD from the University of Nottingham in 1994 and has a background in electronic engineering and computer science teaching and research, including design of communication aids, surgical simulation devices & software, and collaborative virtual environments. Email:

Jennifer L Martin is a MATCH Senior Research Fellow at the University of Nottingham where her interests lie mainly with the application of ergonomics methods to the development and design of medical devices. Jennifer has a PhD in Ergonomics from Loughborough University; her doctoral research was concerned with the design and evaluation of novel load carriage equipment for the Ministry of Defence. Following this, she worked in health services research for a number of years before returning to ergonomics and the topics of medical device development and patient safety. She has also worked at the NHS National Patient Safety Agency where she led the human factors team. Email:

Michael P Craven
Jennifer L Martin
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