Programa de Manejo de Residuos Sólidos y Líquidos

27

2.2.2. User centred design of medical devices

User Centred Design (UCD) is a term to describe a design process whereby the end user influences how the design evolves and meets their needs. The term UCD originated in Donald Normans research laboratory at the university of California San Diego in the 1980s (Abras et al. 2004). Norman built further on the concept of UCD in his seminal book: The Psychology Of Everyday Things (POET). In POET, Norman emphasizes the needs of the user, and the usability of the design. He suggests four basic heuristics to influence design:

 Make it easy to determine what actions are possible at any moment.

 Make things visible, including the conceptual model of the system, the alternative actions, and the results of actions.

 Make it easy to evaluate the current state of the system.

 Follow natural mappings between intentions and the required actions; between actions and the resulting effect; and between the information that is visible and the interpretation of the system state (Norman 1988).

These heuristics place the end user at the centre of the design process. The role of the designer in this process is to ensure that the user is able to use the product to carry out the task with effectiveness, efficiency and satisfaction (Abras et al. 2004). The benefits of UCD are vast and encompass the identification of new ideas, design directions, better user experience, reducing complaints/error, and a more precise definition of functionality (McClelland and Suri 2005). Hallbeck (2010) Portrays UCD as “both a philosophy and a process” and in a review of approaches and standards notes that “most medical devices, including surgical and laparoscopic tools, have not been designed using UCD principles; in fact some appear not to have considered there was a user”.

28

Major advantages of utilising the UCD approach is a deeper and more robust understanding of the psychological, organisational, social, and ergonomic factors that emerge from the involvement of users from the very beginning of, and throughout the product development process. The involvement of real life end-users ensures that the product will fulfil its intended purpose in the scenarios and environment in which it will be used. The UCD approach leads to the development of products that are more effective, efficient and safer (Abras et al. 2004).

ISO-18152 defines user centred design as:

- An approach to design that is characterised by the active involvement of users, a clear understanding of user and task requirements, an appropriate allocation of function between users and technology, iterations of design solutions, and multi-disciplinary design.

Abras et al. (2004) discuss some of the methods that have subsequently been developed to support UCD such as usability testing, usability engineering and participatory design. The standard goes on to address the common held misconception that usability and user centred design are one and the same – ‘usability engineering is often used as a substitute for user centred design. However applying usability engineering methods does not necessarily prescribe the active user involvement that is the essence of user centred design. In addition, usability engineering often over-emphasises the role of evaluation methods. Human-centred design, on the other hand, refers to the process of analysing context of use, eliciting user requirements, producing design solutions and evaluating the design against the requirements, all in an iterative fashion’ (ISO- 18152:2010 Definition 4.8).

It can be said that usability is a measure of success in implementing user centred design.

29

2.2.3. Usability

The term usability was coined in the early 80s in order to replace the term ‘user- friendly’ which had acquired a host of vague and subjective connotations (Bevana et al. 1991). Usability can be described as the “development of devices (products) which are fit for use” (Matern and Büchel 2011). Originally envisioned as a tool to aid and evaluate the design of human-computer interfaces, the application of usability has broadened significantly over the last three decades. In recent years the focus of design has moved from the reduction of physical exertion to the reduction of mental exertion while using a product. It is also important that the product (device) should not distract the users’ attention away from the actual task as a result of the design. Devices which are intuitive, easy to use and satisfying are described as usable. Usability is a qualitative attribute that indicates how easy a product is to use (Matern and Büchel 2011). Telling designers that a device should be intuitive is not enough, therefore design principles are necessary to guide them (Abras et al. 2004). Norman (1988) Put forward ‘seven principles of design […] essential for facilitating the designer’s task’. Normans work concentrated on the necessity to explore needs and desires of the intended users fully. The need to involve actual users in real world scenarios and environments during every stage of the design process was a natural evolution of the concept of user centred design. Nielsen (1993) Adapted and popularised Normans design principles by stressing the importance of considering usability as a multifaceted approach, describing five usability attributes: Learnability, efficiency, memorability, errors, and satisfaction.

The application of HF to the design of medical devices strives to deliver robust, safe and effective products to the market. To ensure this, usability testing is prescribed in the relevant standards throughout the design process of medical devices, and is discussed in the following sections.

30

2.3. Usability testing of medical devices during design

Medical device users are an extremely heterogeneous group. They range from exclusively physicians, to nursing staff, support staff, patients, to their family and carers. Measuring and fulfilling user requirements during medical device development results in successful products that improve patient safety, improve device effectiveness and reduce product recalls and modifications (Jennifer et al. 2006). Usability testing should not be considered as product validation. Usability testing can verify that the design outputs and design inputs correspond; that is that the design solution encompasses all of the design specifications stated at the beginning of the project. Medical device validation should include laboratory testing to evaluate device efficacy, reliability, safety and performance before clinical testing (Weinger et al. 2010).

The need for usability testing is mandated in the US by the FDA in 21 CFR 820