Medical device usability as a factor in reducing error and improving outcomes

Human factors are key inputs in the design of medical devices, especially with the increasing number aimed at patient use in the home. Kay Sinclair & Natalie Scott of Sagentia outline the issues involved and the implications of new standards aimed at usability.

4 April 2011

The new set of human factors standards that were introduced in 2010 (HE75, the new ANSI/AAMI standard and the IEC62366) aim to address the high number of medical device incidents that involve usability issues.

By requiring companies to track user feedback and justify proposed use error mitigation approaches, regulators are emphasising the important role that usability plays in product safety.

These new regulations also recognise the fact that, as some therapies transition away from clinical environments, medical devices are increasingly being used by a patient population that has less experience and training.

In addition to promoting safety, integrating usability into a product development programme is quite simply good design practice. In fact, a good way of adhering to the new standards is to:

  1. take a holistic view of usability and incorporate it as a key component of every product development programme; and
  2. make sure that the specific market demands for each new product are understood from the outset.

Why spend time on usability?

If people are involved in the use of a product, then human factors should be core to that product’s development process. This is especially relevant in the medical field where device manufacturers need to improve patient compliance, prove effectiveness and reduce safety risks.

For example, a diabetic who needs to take his or her medication while at a restaurant will probably want something that is discreet, fast and can be done — with one hand. An appropriately designed insulin device will promote correct use and encourage regular and maintained use of the device.

The fundamental goals of a medical device product development programme are that the product works, is reliable for manufacturing, meets end usage objectives and achieves target commercial return.

Although good usability design directly supports all three of these goals, it is often sidelined, delayed or considered to be an add-on to technical development. When properly integrated, however, usability reviews provide the essential insight to balance, help challenge, inform and direct technical decisions throughout the development lifecycle. This leads to streamlined manufacturing, a good user experience and better prospects for sound commercial return.

In extreme cases, poor usability can lead to product recalls which are costly to rectify, and can also have a damaging effect on a company’s technical and corporate reputation. The converse is also true: a company that gains a positive reputation for the usability of its products will benefit from increased customer loyalty, reputation and hence sales across its entire product portfolio.

What's your approach to human factors?

Outlined below are three groups of usability tools that should be considered as part of any product development programme.

Context exploration

Context exploration tools help define and understand the target user(s) and their use environments. This will involve task analysis and the exploration of use scenarios, potential user errors and hazards.

Exploring capability should also be a key part of human factors. This involves exploring the physical, cognitive and sensory boundaries of each user profile and should be used as a framework throughout user testing. There are seven capability scales that can be used in isolation to explore and improve the usability of a device or concept.

User perspective exploration

User study tools can take different guises but the aim is to explore potential use errors and hazards, user preference and instinct, physical and cognitive demand, user performance and capability boundaries, etc. This should include all influencing users and a cross section of each user type as appropriate (ie patients, care givers, health professionals, etc).

Justification and documentation

All FDA documentation now needs to include an explanation of the company’s plan for managing and mitigating possible risks. There are many tools that can be used to address this requirement. A single document approach to tag and trace all potential usability issues is perhaps amongst the best. Regardless of format, companies will need to justify their device decisions from the perspective of the user.

In the past, the FDA may have accepted a design goal that “80% of users must be able to open the device first time”, they now want to know more about the 20% that couldn’t — what they did, why and what is the resulting safety risk. A plan to mitigate or control expected or actual usage error will also be required.

How do you integrate usability activities into your current product development programme?

Human factors can be a key but flexible part of your product development process. This can range from having a usability expert challenge the product development at appropriate points, to a more integrated approach that uses human factors tools throughout the development process.

The main rule is that the specific nature and objectives of each device is first understood. Deciding on the type, shape and size of the human factors tools to use will then depend on a number of factors. The following questions can help determine which tools to use and how to use them:

  • is this a completely new device for a new market or a redesign of an existing device in a highly populated market?
  • what is the complexity of the user interaction?
  • what is the potential for and severity of harm that can be caused by interacting with the device?
  • what is the time and resources available to complete the development?

The impact of the new standards themselves will vary depending on your current approach to usability. If human factors are not already significantly incorporated into your approach, the new standards should guide the tools you choose and how they integrate into your process. Alternatively, should human factors be current practice, these standards may simply direct how you document, trace and justify the risk of potential usage error.

Usability issues in medical device sectors

Integrating human factors research into medical device design can vary considerably depending on the device being developed, the device category and the product’s specific objectives.

Critical care

The usability of devices and equipment in the critical care sector has always been of paramount importance. However, with the current trend towards moving the treatment of many chronic conditions out of the hospital and into the home means that the challenge facing manufacturers of critical care equipment is even more extreme.

Manufacturers need to consider how best to design for the future, where the user may not be a highly trained nurse or technician, and the environment may not be quiet, clean and closely supervised.

The FDA is pushing for this to be a consideration now, even if the current generation of the device is designed specifically for the hospital only. The aim is partly to save the time and cost of subsequent product iterations for the home market, but more importantly to prevent the inevitable safety risks that will result from using a device that has not been designed for an untrained user group or the home environment.

Drug delivery

Drug delivery devices for personal use are well established. Pharmaceutical companies are now not only focusing on device performance and functionality but are also looking at device usability as a primary differentiator.

For example, insulin pens have been available since the early eighties and have evolved significantly over this time; starting from a new exciting drug delivery approach with limitations, to a focus on reliability and performance improvements, to more recently an emphasis on usage improvements.

As with most drug delivery devices launched today, understanding the range of patient profiles, the different attitudes towards treatment, the varying years of experience and the differing scenarios of use (amongst other characteristics) is key to a product’s success.


The main trend in clinical diagnostic testing is the move away from central laboratory testing to the point of care in the clinical market. Some of these tests are already routinely used in the home environment (eg blood glucose monitoring). Although these diagnostics, and their results, are ultimately prescribed by the healthcare professional, the devices themselves are increasingly operated by the patient.

With the move towards the less skilled, and eventually, patient use environment there are a number of usability factors to consider:

  • understanding how the user interacts with the device;
  • managing how the user understands, reacts and responds to the result;
  • ensuring the reliability of the device and the result, given the variability of use conditions.

Whilst these are not insignificant challenges to overcome, there are also additional points to consider. For example, the ethical question of the types of diagnostic testing that should be patient-driven. Where should the line be drawn between providing devices that help people take control of their own health and manage their wellbeing and assisting the worried well to self test, diagnose and treat themselves?

Certain invasive diagnostic procedures and disease-specific diagnoses will and should always remain in the hands of the healthcare professionals. However, where there are diagnostic tests and devices that will have a positive clinical impact by moving away from clinical practitioners to patient self-use, human factors will become an essential part of any potential development.


Surgical devices are used by highly trained medical specialists, which results in the potential benefits of usability analysis often being underestimated. However, in the often hectic environment of the operating theatre, any interaction with the device that diverts the attention of the medical specialists away from the patient is an opportunity for improvement.

Examples of such situations are numerous and take many forms: Optical aids such as surgical microscopes that are difficult to adjust, buttons on devices that require the surgeon to change their grip during the surgery or minimally invasive devices without articulations that require the surgeon to adopt an uncomfortable position.

Packaging for disposable devices is another area, often overlooked, which should be designed to make the transaction between theatre staff and surgeon as easy and seamless as possible.

Two further trends that are putting new demands on usability are the growth in robotic surgery, where the surgeon needs to comfortably operate a remote control, and the increased use of navigational technology in operating theatres, where physical interaction with the navigation system and associated visual cues are key and currently a foreign experience for the surgeon.

A standard approach

To date, human factors research has often been seen as an activity that could be sidelined if budgets and time are too constraining. However, the new standards are putting an end to this view.

A company that views usability as an integral part of their design practice should find that the new standards require them to simply document and justify their existing approach. In essence, therefore, the standards should support the growing awareness that the integration of usability work in the development process is just good design practice that leads to better, safer and more usable products. Device companies that understand this are also gaining competitive advantage by offering differentiated and desirable products.

In order to ensure that an effective and efficient approach is taken to usability, it is important to understand each specific development programme’s use criteria and then identify the best tools to use.

Different medical device sectors have varying needs and drivers for human factors that will lead to different emphases. One thing that is consistent, however, is that human factors research is growing in importance, and will continue to do so, across all medical device sectors.

Kay Sinclair, Managing Consultant, Sagentia Ltd.
Natalie Scott, Consultant, Sagentia Ltd.


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