Generating Phenotypical Erroneous Human Behavior to Evaluate Human-automation Interaction Using Model Checking

Masking Between Reserved Alarm Sounds of the IEC 60601-1-8 International Medical Alarm Standard: A Systematic, Formal Analysis

OBJECTIVE

In this work, we systematically evaluated the reserved alarm sounds of the IEC 60601-1-8 international medical alarm standard to determine when and how they can be totally and partially masked.

BACKGROUND

IEC 60601-1-8 gives engineers instruction for creating human-perceivable auditory medical alarms. This includes reserved alarm sounds: common types of alarms where each is a tonal melody. Even when this standard is honored, practitioners still fail to hear alarms, causing practitioner nonresponse and, thus, potential patient harm. Simultaneous masking, a condition where one or more alarms is imperceptible in the presence of other concurrently sounding alarms due to limitations of the human sensory system, is partially responsible for this.

METHODS

In this research, we use automated proof techniques to determine if masking can occur in a modeled configuration of medical alarms. This allows us to determine when and how reserved alarm sound can mask other reserved alarms and to explore parameters to address discovered problems.

RESULTS

We report the minimum number of other alarm sounds it takes to both totally and partially mask each of the high-, medium-, and low-priority alarm sounds from the standard.

CONCLUSIONS

Significant masking problems were found for both the total and partial masking of high-, medium-, and low-priority reserved alarm sounds.

APPLICATION

We show that discovered problems can be mitigated by setting alarm volumes to standard values based on priority level and by randomizing the timing of alarm tones.

A Formal Analysis of Masking Between Reserved Alarm Sounds of the IEC 60601-1-8 International Medical Alarm Standard

The IEC 60601-1-8 international medical alarm standard was created to give engineers guidance for designing alarms that are easily perceivable by humans. Included within this are a number of reserved alarm sounds that use tonal melodies to represent common types of alarms. Despite the standard, practitioners can still fail to hear and respond to alarms. This can have a profound negative impact on patient life and health. One of the factors that contributes to this problem is simultaneous masking: a condition where one or more alarms can be rendered imperceptible in the presence of other alarms due to limitations of the human perception system. Unfortunately, the tonal nature of the IEC 60601-1-8 reserved sounds makes them particularly susceptible to masking. It can be difficult to determine how masking can manifest in a collection of alarms that can sound concurrently given the inherent complexity of the statespace. In this work, we employ a computational method that employs mathematical proof techniques to determine if masking is possible in a model of a configuration of medical alarms. We use this to analyze the low and medium priority reserved alarm sounds of the IEC 60601-1-8 standard. We describe our method, present the results of our analyses, discuss these results, and explore future research directions.

Novel Developments in Formal Methods for Human Factors Engineering

Formal methods are robust tools and techniques for modeling, specifying, and mathematically proving properties about (verifying) systems. They are particularly good at both finding unexpected problems that arise from complex system interactions and proving that specific types of problems will never manifest. Formal methods have predominantly been used in the analysis and design of computer hardware and software systems. However, a growing research area within the human factors engineering community has been examining how formal methods can be used to prove whether problems exist in systems that rely on human-automation and human-human interaction for their safe operation. This symposium contains four papers by researchers who have been pushing the boundaries of where and how formal methods can be used in human factors engineering.

A formal approach to discovering simultaneous additive masking between auditory medical alarms

The failure of humans to respond to auditory medical alarms has resulted in numerous patient injuries and deaths and is thus a major safety concern. A relatively understudied source of response failures has to do with simultaneous masking, a condition where concurrent sounds interact in ways that make one or more of them imperceptible due to physical limitations of human perception. This paper presents a method, which builds on a previous implementation, that uses a novel combination of psychophysical modeling and formal verification with model checking to detect masking in a modeled configuration of medical alarms. Specifically, the new method discussed here improves the original method by adding the ability to detect additive masking while concurrently improving method usability and scalability. This paper describes how these additions to our method were realized. It then demonstrates the scalability and detection improvements via three different case studies. Results and future research are discussed.

Beyond the VAD: Human Factors Engineering for Mechanically Assisted Circulation in the 21st Century

Thousands of ventricular assist devices (VADs) currently provide circulatory support to patients worldwide, and dozens of heart pump designs for adults and pediatric patients are under various stages of development in preparation for translation to clinical use. The successful bench-to-bedside development of a VAD involves a structured evaluation of possible system states, including human interaction with the device and auxiliary component usage in the hospital or home environment. In this study, we review the literature and present the current landscape of preclinical design and assessment, decision support tools and procedures, and patient-centered therapy. Gaps of knowledge are identified. The study findings support the need for more attention to user-centered design approaches for medical devices, such as mechanical circulatory assist systems, that specifically involve detailed qualitative and quantitative assessments of human-device interaction to mitigate risk and failure.

Designing and optimizing a healthcare kiosk for the community

Investigating new ways to deliver care, such as the use of self-service kiosks to collect and monitor signs of wellness, supports healthcare efficiency and inclusivity. Self-service kiosks offer this potential, but there is a need for solutions to meet acceptable standards, e.g. provision of accurate measurements. This study investigates the design and optimization of a prototype healthcare kiosk to collect vital signs measures. The design problem was decomposed, formalized, focused and used to generate multiple solutions. Systematic implementation and evaluation allowed for the optimization of measurement accuracy, first for individuals and then for a population. The optimized solution was tested independently to check the suitability of the methods, and quality of the solution. The process resulted in a reduction of measurement noise and an optimal fit, in terms of the positioning of measurement devices. This guaranteed the accuracy of the solution and provides a general methodology for similar design problems.

Socio-Technical Systems Analysis in Health Care: A Research Agenda

Given the complexity of health care and the 'people' nature of healthcare work and delivery, STSA (Sociotechnical Systems Analysis) research is needed to address the numerous quality of care problems observed across the world. This paper describes open STSA research areas, including workload management, physical, cognitive and macroergonomic issues of medical devices and health information technologies, STSA in transitions of care, STSA of patient-centered care, risk management and patient safety management, resilience, and feedback loops between event detection, reporting and analysis and system redesign.