The problem encountered by TIM Solutions was mainly based on experiences of their own in different hospitals. The project was therefore started with mapping the wishes of possibile users and mapping the current context. Already in the beginning it turned out that fluid balance measurements are well based estimations as not all aspects are being monitored and recorded. Aspects like sweating, vomitting, heavy diarrhoea were not taken into account. Frustrations about the paper fluid lists getting lost, not knowing when to replace intravenous (IV) bags and communication between different care takers became clear. The different departments more or less created a way to work aournd the issues. For example, replacing of IV bags at the geriatrics department was sometimes done far before the bag was really empty to avoid forgetting to replace it. This means that the old IV bag will be thrown away before it is fully used.

Another important aspect was the division in responsibility around registering the fluid balance. It turned out that there is a big difference between involving the patient and giving the patient responsibility. Involvement is preferred by both patient and nurse, but responsibility needs to be avoided at all times. Most patients from whom an (hourly) fluid balance overview is required are quited ill and therefore incapable (mentally or physically) to take over tasks that contribute to their recovery. Patients need to have insight in how to contribute to a quicker recovery in a positive way (involvement), but the nurse is responsible in the end.

The product-service-system was divided in different system parts. These different system parts were eventually combined to several concepts that were discussed with multiple nurses at the following wards of the UMCG: geriatrics, nephrology, cardiology and intensive care. Furthermore three nurses from the Haga hospital and the RDGG provided feedback throughout the process.

Most wards preferred to have a product-service-system that is being controlled by the nurse (and assistant) and can be used by the patient when the nurse approves. The final product-service system consists of one tablet (including tablet holder), one adapter, multiple hooks and multiple FluidBalance hangers.

Interaction wise it was prefered to assemble as much functionality into one place at an ergonomic height, meaning that the FluidBalance hanger only requires interaction when (un)installing. Further interaction will happen on the FluidBalance tablet and computer on wheels (COW).

The FluidBalance hangers will gather information about their attached bags. This information will be send to the tablet using Wi-Fi. The tablet will be a central entrance point for all other gained and lost fluids and will calculated the patient’s fluid balance. This information will be send to the COW which means that it will be added to the patients electronic hospital file (EPD). (figure 1)

After defining the overall product-service-system the focus shifted to the conceptualisation and embodiment of the FluidBalance hanger. Both internal and external embodiment were investigated and tested. Several prototypes were used to investigate: accuracy, how to control influences due to movement of the patient, how to attach the product somewhere around the patient’s bed and how to compile the right components to make sure that the product will last for a few months. Findings based on interviews with nurses and trials with different Arduino codes have led to the first working model of the FluidBalance hanger (figure 1).