Is it Possible to Interact with a Handheld Device While Holding it in Both Hands?

Intuitiveness, attractiveness and efficiency are in general important characteristics of high quality User Interfaces (UI). In the case of a Mass Casualty Incident (MCI) and other life threatening situations good user interfaces are essential as every second counts in these time-critical situations. Finding the best way to interact with the system is a challenge with many open issues. Therefore, it is essential to test different UI alternatives to determine important usability issues as those mentioned before. This paper focuses on the research question how patients can be selected on a map application which runs on a rugged tablet PC. A rugged tablet PC is in general heavy because of its robustness, which introduces a new special requirement in addition to the existing UI requirements. Consequently, since the users are forced to hold the tablet PC with two hands because of its heaviness, they have to perform all UI interaction with the thumbs. This implies that the users are not able to reach every item on the screen of the tablet PC. Therefore all UI elements have to be either on the left or on the right hand-side of the screen. The implementation and the evaluation of the UI alternatives presented in this paper were performed within the scope of the SpeedUp project. 1 Motivation Usability brings order in the chaos? A Mass Casualty Incident (MCI) is an incident which generates more patients than the locally available rescue workers can manage simultaneously. The medical rescue teams have to face a vehement organizational challenge in such disasters. Since there are too many injured people to handle at once, they need to be categorized. This categorization is done by the relief units executing a triage algorithm such as the Simple Triage and Rapid Treatment START during the first triage [MKC96]. This is a deterministic way to define the priority and the need of each patient to benefit from medical care. There is already an ongoing research which digitizes the triage approach using PDAs [NK07]. Using PDAs equipped with GPS sensors has the advantage to track the position of the patients. The PDAs are supposed to be used by the relief units in the field. The tracking positions are 1The project SpeedUp is funded by the German Federal Ministry of Education and Research (BMBF) within the program ”Research for Civil Security” (May 1st, 2009 April 30th, 2012, FKZ: 13N10175). Website: http://www.speedup-projekt.de transferred from the distributed PDAs in the field to the tablet PC used for this work. The positions of the patients are visualized in an overview map on the tablet PC in the scope of this work. This paper focusses on the second triage. It is done by the Emergency Medical Chief (EMC) or an emergency doctor appointed by the EMC. During this second step the patients are more precisely re-categorized if necessary and the succession of patients ́ transportation to the nearest hospital will be determined by the EMC. Currently, the EMC is getting this information from the rescue units verbally. The number of injured people and their classification are written down by the relief units on paper. So this information can be incomplete, redundant and/or wrong. Obviously, using an IT solution can improve and introduce order in the chaotic situation in such incidents. This is why we propose that the EMC should use the tablet PC to acquire the required information about the patients. However, because of the users’ tendency to resist or even reject new technologies with inadequate user interfaces or bad usability, all conceivable improvements can be useless. It is therefore essential to develop the user interface closely with the user to find out which UI alternative is the most intuitive, efficient and attractive. To achieve that, we investigate first touch user interfaces, because of the fact that the UI has to fulfill the UI requirements coming from touchscreen devices. This is described in section 2. Additionally, more special requirements on the user interface suitable for an MCI situation have to be considered and explored. This paper focuses on designing a usable UI to select items (patients or relief units for instance) fulfilling these special UI requirements. Those special requirements are going to be mentioned in section 3.2.