Simulation to evaluate alternative approaches to blocking use errors

Unnoticed user slips may contribute to adverse events, but medical devices can be designed to help detect and block some slips, thus enabling the user to take corrective action. Obviously different designs achieve this with greater or lesser success [1]. This paper shows how comparison of alternative design features for a “5-key ” user interface (figure 1) can help reduce number entry errors. 5-key interfaces are widely-used because they look intuitive and require very little physical space. Method We compare a typical commercial design, the 5-key hours/minutes user interface of the Zimed AD Ambula-tory Syringe Driver, with alternatives that: (1) start with the cursor at the far left or far right; (2) make the / buttons change the value by ±1 in the relevant numbe