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Modelling and analysis of
interoperable medical systems using PVSio-web

Key Points

  • We have developed new tools for verification and validation of interoperable medical systems
  • The tools are part of our PVSio-web prototyping environment for interactive (human-computer) systems
  • They have been successfully used to develop a realistic interoperable medical system prototype based on commercial products and application scenarios described by the FDA
  • They will be used to validate the FDA requirements for interoperable medical systems

Interoperable Medical Systems
Medical devices have communication capabilities that can be exploited for improving the safety and effectiveness of medical systems. For example, consider a clinical situation where an infusion pump is infusing opioids to a patient. A patient monitor analysing the patient's conditions could alert the nurses if the patient enters respiratory depression, and at the same time immediately stop the infusion of the opioid, thus saving the patient's life.

The benefits of interoperable medical devices are clear. However, careful design decisions need to be taken to ensure safety of operation. For example, with reference to the previous example, what happens if the patient monitor is configured incorrectly, or operated incorrectly, or malfunctioning? It is certainly desirable that the infusion pump operates as safely as in a situation when the pump is not connected to the patient monitor.

Regulators such as the Food and Drug Administration are promoting the use of model-based engineering techniques to explore design solutions and identify design defects in advance [ray2010]. The process is based on the idea of creating mathematical models that describe the behaviour of the real system, and then analyse these models to gain confidence that the real system can operate safely. The advantage of this process is that developers can use it from the early stages of development (a full physical prototype of the device is not needed), and enables rapid and precise exploration of different alternative solutions and different scenarios.

Our new PVSio-web extension
We present our ongoing work on extending our rapid prototyping tool PVSio-web [pvsio-web] to support model based-engineering of interoperable medical systems. The tool has been successfully used to develop generic infusion pump prototypes [masci2013], as well as to identify defects in real devices [masci2014a, masci2014b]. We are introducing a new mechanism in the tool that allows developers to install virtual communication ports on device prototypes developed using PVSio-web. Using these virtual ports, device prototypes can be connected to real communication networks, and thus use real communication protocols to exchange data and commands with other devices connected to the same network. This mechanism therefore enables creating realistic prototypes of interoperable systems that include both PVSio-web prototypes and real devices (e.g., physical prototypes, or final products).

Application and Impact
We have developed a demonstrative prototype of an interoperable medical system with an infusion pump prototype and a patient monitor prototype. The two prototypes are executed on two different physical machines, and they exchange data and commands using an open communication service for mobile devices.

Future work includes developing new demonstrative prototypes based on the Medical Application Platform [larson2012] architecture developed by the FDA in collaboration with other universities for the analysis of requirements for interoperable medical systems.

[ray2010] Ray, A. and Jetley, R. and Jones, P. and Zhang, Y., Model-Based Engineering for Medical-Device Software, Biomedical Instrumentation & Technology, volume 44(6), pages 507--518, 2010

[pvsio-web] Oladimeji, P. and Masci, P. and Curzon, P. and Thimbleby, H., PVSio-web: A tool for rapid prototyping device user interfaces in PVS, in Proceedings of 5th International Workshop on Formal Methods for Interactive Systems (FMIS2013), 2013. Tool and examples available at http://www.pvsioweb.org

[masci2013] Masci, P. and Ayoub, A. and Curzon, P. and Lee, I. and Sokolsky, O. and Thimbleby, H., Model-Based Development of the Generic PCA Infusion Pump User Interface Prototype in PVS, in Proceedings of Computer Safety, Reliability, and Security (SafeComp2013), Lecture Notes in Computer Science, pages 228-240, Springer Berlin Heidelberg, 2013, http://dx.doi.org/10.1007/978-3-642-40793-2_21

[masci2014a] Masci, P. and Zhang, Y. and Jones, P. and Curzon, P. and Thimbleby, H., Formal Verification of Medical Device User Interfaces Using PVS, in Proceedings of 17th International Conference on Fundamental Approaches to Software Engineering (ETAPS/FASE2014), Springer-Verlag, 2014

[masci2014b] Masci, P. and Oladimeji, P. and Curzon, P. and Thimbleby, H., Tool demo: Using PVSio-web to demonstrate software issues in medical user interfaces, in Proceedings of 4th Intl. Symposium on Foundations of Healthcare Information Engineering and Systems (FHIES2014), 2014

[larson2012] Brian Larson, John Hatcliff, Sam Procter, Patrice Chalin, Kansas State University. Requirements Specification for Apps in Medical Application Platforms, in Proceedings of 4th International Workshop on Software Engineering in Health Care (SEHC), pages 26-32, 2012, http://dx.doi.org/10.1109/SEHC.2012.6227013