What To Do When The Requirements Are Unknown? - Development of a Simulator for Excretory Care

We developed a simulator to practice the digital disimpaction technique, a kind of excretory care that is commonly performed by home-care nurses in Japan. The key point of this study is that the requirements for creating a simulation model were not known in advance, so we adopted a rapid prototyping method, in which product development is carried out by repeatedly creating and testing simple prototypes and a user-participatory design method, where feedback is obtained directly from users. We proceeded with the development of the simulator and the definition of requirements simultaneously, repeating the process of creation, trial use, and feedback from interviews with skilled nurses. Digital disimpaction is a complex procedure involving interaction with a living body, in which a finger stimulates the rectum and facilitates the excretion of feces leveraging the rectum's natural biological response. Digital disimpaction is performed primarily by a nurse. Since digital disimpaction is an embarrassing and sometimes painful procedure for the patient, a smooth and comfortable technique is desirable. On the other hand, only a limited set of circumstances are provided to learn the digital disimpaction technique. The requirement for a "procedure requiring non-visible interaction," such as digital disimpaction, is hard to acquire through a simple interview because it is performed based on subjective sensation. Further, while the movement of the finger within the body is crucial, it is essentially impossible to learn through observation of a skilled nurse as it is not visible from the outside. For this reason, we created a simple rectal model as a first prototype. We improved the model by extracting requirements from observations and feedback on actual trial use by skilled nurses. From the first user experience of the simple 3D printed model, requirements were extracted regarding the texture of the rectum, the interaction between finger movement and rectal response, and the characteristics of the feces. A rectal model with a mucosal structure and a fecal model was created based on the obtained requirements. Through the second user experience, the process was repeated, where requirements were again extracted regarding the shape of the rectal model, the characteristics of the mucosa, and the rectal response with the finger movement. We redesigned the model to meet these refined requirements and developed a buttock model covering the rectal model.The results of the third user experience confirmed that the simulator mostly reproduced the intestinal setting as perceived by the nurses during the actual digital disimpaction procedure. This study suggests that the combination of rapid prototyping and user-participatory design can be used to systemize subjects for which requirements are hard to define in advance, such as care procedures based on tacit knowledge.