Using medical device logs for improving medical device design

User interfaces that employ the same display and buttons may look the same but can work very differently depending on exactly how they are implemented. In healthcare, it is critical that interfaces that look the same are the same. Hospitals typically have many types of visually similar infusion pumps, but with different software versions and variation between pump behavior, and this may lead to unexpected adverse events. For example, when entering drug doses into infusion pumps different results may arise when pushing identical sequences of buttons. These differences arise as a result of subtle implementation differences and may lead to large errors users do not notice. Previous work has explored different implementations of a 5-key interface for entering numbers using a new analysis technique, Differential Formal Analysis, where predictions relating to the distribution of errors in terms of the size of the error (out by 10, out by 100 and so on) can be made. The analysis described in the paper extends this work with models of use based on many hours of actual clinical use data. Specifically, we draw on 1,362 days of use of number entry systems, from 19 infusion pumps over a 3 year period in a UK hospital. The paper also suggests some improvements to medical device logs, which will help further evidence-based improvement to medical device safety.