## 5 FULE Methodology
### Phase 2: Usability  
During the development process of a new medical device, attention is primarily focused on specifications that guarantee proper functionality. However, technical and functional specifications usually do not fully and thoroughly consider user needs or guarantee easy and safe usage [18]. Thus, technological products, even innovative and cutting-edge ones, might fail in the market when the design does not match human needs, cognitive processes, or the work environment [19]. The second phase, usability, refers to product features that would help users achieve their goals effectively and efficiently (ISO 9241-11). This phase is divided into four sub-phases: learning, analyzing, defining, and ideating. Here, significance in the product development process (and especially in the design of medical devices) cannot be underestimated. Poor usability may result in high costs, wasted  
Figure 3: The functionality phase is divided into three sub-phases. time, increased need for service calls and training, and decrease staff morale and productivity [20]. The understanding that design can prevent the user from making mistakes (or at least minimize them) is relatively new. In the past, it was customary to resolve usage faults by adding a warning to the operator's manual or a warning sticker on the product itself. Over time, it was recognized that if a trained user (a nurse or doctor) makes a mistake with a device, there is likely a design problem rather than a user problem. Walking through hospital corridors can illustrate the importance of the development process' usability stage and reveal various pieces of evidence of events resulting from misuse; each product warning sticker tells a story. This understanding also influenced the Food and Drug Administration (FDA) regulators to emphasize human factors and usability and add tests for this before giving new systems approval. In 1997, the first FDA manual addressing medical device development professionals, _Do it by design: An Introduction to Human Factors in Medical Devices_[6], was published. The booklet provides a concise explanation of basic concepts such as physical and sensual characteristics, perceptual and cognitive abilities, and mental models. In addition, the booklet contained case descriptions from the Medical Device Reporting System [21], a system into which details of events that ended in injury to the body or mind are entered. According to the methodology proposed by the FDA, in an ideal situation, hardware and software designers, engineers, human factors personnel, document writers, and clinical staff coordinate their efforts to achieve a user interface design that ensures speed, convenience, and safety at every stage of a product's life: assembly, installation, use, and maintenance. The usability phase of the FULE methodology uses the main principles described by the FDA. The phase consists of four sub-stages: the first two about learning and analysis, and the other two about settings, planning, and creating, as illustrated in Figure 4.  
The first stage is _learning_. The designer must clearly understand the new design's goal and become familiar with the medical condition and the offered solution. In this stage, the designer defines all users (patient, specialist, nurse, family, informal caregivers, etc.) and understands the environmental conditions (physical environment, social environment, and ambient conditions). The tools we use for the learning stage are varied and may differ from project to project. Still, they will always include examining an existing/similar system (if any), interviews with the various users, and observations in the work environment and similar procedures. Additional tools may be anonymous questionnaires, pollination (searching for ideas in tangential or other content worlds), a literature review, and consulting with experts from various fields. After collecting the data, we perform the _analysis_ phase by building task sequence models and usage scenarios.