Sandy Weininger

An open test bed for medical device integration and coordination

Medical devices historically have been monolithic units — developed, validated, and approved by regulatory authorities as stand-alone entities. Modern medical devices increasingly incorporate connectivity mechanisms that offer the potential to stream device data into electronic health records, integrate information from multiple devices into single customizable displays, and coordinate the actions of groups of cooperating devices to realize “closed loop” scenarios and automate clinical workflows. However, it is not clear what middleware and integration architectures may be best suited for these possibly numerous scenarios. More troubling, current verification and validation techniques used in the device industry are not targeted to assuring groups of integrated devices. In this paper, we propose a publish-subscribe architecture for medical device integration based on the Java Messaging Service, and we report on our experience with this architecture in multiple scenarios that we believe represent the types of deployments that will benefit from rapid device integration. This implementation and the experiments presented in this paper are offered as an open test bed for exploring development, quality assurance, and regulatory issues related to medical device coordination.

Development of a standardized method for motion testing in pulse oximeters.

BACKGROUND:Pulse oximeter performance in the presence of motion varies among devices and manufacturers because of variations in hardware, software, testing, and calibration. Compounding these differences is a lack of uniform characterization of motion, and the consequential effects of motion upon the wide range of normal and abnormal human physiology. Traditional motion testing attempts to standardize motion into a reproducible form by using a mechanical jig to produce passive motion of a known amplitude and frequency. This type of motion challenge fails to account for the physiologic changes induced by active movement. METHODS:We postulate that a more appropriate method for testing the performance of pulse oximeters in the presence of motion is to create a feedback control loop between the device and the test subject, providing a reproducible, actively created, and controlled motion test suitable for standardized testing among manufacturers. It is hoped that relying on a signal as seen from the oximeters perspective will enable the creation of a sensitive and reproducible test method capable of separating those oximeters that can reject motion artifact from those that cannot. RESULTS:Preliminary results have concentrated on building the tools and clinical protocols needed to evaluate this method. Some basic observations are reported, but insufficient numbers of experienced subjects precludes rigorous conclusions. CONCLUSION:We have set the stage for a feasibility demonstration using a novel form of testing. With sufficient subjects and proper statistical evaluation, a robust test method for assessing the performance of pulse oximeters in the presence of motion may be at hand.

Regulatory perspectives and research activities at the FDA on the use of phantoms with in vivo diagnostic devices

For a number of years, phantoms have been used to optimize device parameters and validate performance in the primary medical imaging modalities (CT, MRI, PET/SPECT, ultrasound). Furthermore, the FDA under the Mammography Quality Standards Act (MQSA) requires image quality evaluation of mammography systems using FDA-approved phantoms. The oldest quantitative optical diagnostic technology, pulse oximetry, also benefits from the use of active phantoms known as patient simulators to validate certain performance characteristics under different clinically-relevant conditions. As such, guidance provided by the FDA to its staff and to industry on the contents of pre-market notification and approval submissions includes suggestions on how to incorporate the appropriate phantoms in establishing device effectiveness. Research at the FDA supports regulatory statements on the use of phantoms by investigating how phantoms can be designed, characterized, and utilized to determine critical device performance characteristics. These examples provide a model for how novel techniques in the rapidly growing field of optical diagnostics can use phantoms during pre- and post-market regulatory testing.

The Need to Apply Medical Device Informatics in Developing Standards for Safe Interoperable Medical Systems.

Medical device and health information technology systems are increasingly interdependent with users demanding increased interoperability. Related safety standards must be developed taking into account these systems’ perspective. In this article, we describe the current development of medical device standards and the need for these standards to address medical device informatics. Medical device information should be gathered from a broad range of clinical scenarios to lay the foundation for safe medical device interoperability. Five clinical examples show how medical device informatics principles, if applied in the development of medical device standards, could help facilitate the development of safe interoperable medical device systems. These examples illustrate the clinical implications of the failure to capture important signals and device attributes. We provide recommendations relating to the coordination between historically separate standards development groups, some of which focus on safety and effectiveness and others focus on health informatics. We identify the need for a shared understanding among stakeholders and describe organizational structures to promote cooperation such that device-to-device interactions and related safety information are considered during standards development.

The Importance of State and Context in Safe Interoperable Medical Systems

This paper describes why “device state” and “patient context” information are necessary components of device models for safe interoperability. This paper includes a discussion of the importance of describing the roles of devices with respect to interactions (including human user workflows involving devices, and device to device communication) within a system, particularly those intended for use at the point-of-care, and how this role information is communicated. In addition, it describes the importance of clinical scenarios in creating device models for interoperable devices.This paper describes why “device state” and “patient context” information are necessary components of device models for safe interoperability. This paper includes a discussion of the importance of describing the roles of devices with respect to interactions (including human user workflows involving devices, and device to device communication) within a system, particularly those intended for use at the point-of-care, and how this role information is communicated. In addition, it describes the importance of clinical scenarios in creating device models for interoperable devices.

Error Type Refinement for Assurance of Families of Platform-Based Systems

Medical Application Platforms (MAPs) are an emerging paradigm for developing interoperable medical systems. Existing assurance-related concepts for conventional medical devices including hazard analyses, risk management processes, and assurance cases need to be enhanced and reworked to deal with notions of interoperability, reuse, and compositionality in MAPs.

Capturing Essential Information to Achieve Safe Interoperability.

In this article, we describe the role of “clinical scenario” information to assure the safety of interoperable systems, as well as the system’s ability to deliver the requisite clinical functionality to improve clinical care. Described are methods and rationale for capturing the clinical needs, workflow, hazards, and device interactions in the clinical environment. Key user (clinician and clinical engineer) needs and system requirements can be derived from this information, therefore, improving the communication from clinicians to medical device and information technology system developers. This methodology is intended to assist the health care community, including researchers, standards developers, regulators, and manufacturers, by providing clinical definition to support requirements in the systems engineering process, particularly those focusing on development of Integrated Clinical Environments described in standard ASTM F2761. Our focus is on identifying and documenting relevant interactions and medical device capabilities within the system using a documentation tool called medical device interface data sheetsa and mitigating hazardous situations related to workflow, product usability, data integration, and the lack of effective medical device-health information technology system integration to achieve safe interoperability. Portions of the analysis of a clinical scenario for a “patient-controlled analgesia safety interlock” are provided to illustrate the method. Collecting better clinical adverse event information and proposed solutions can help identify opportunities to improve current device capabilities and interoperability and support a learning health system to improve health care delivery. Developing and analyzing clinical scenarios are the first steps in creating solutions to address vexing patient safety problems and enable clinical innovation. A Web-based research tool for implementing a means of acquiring and managing this information, the Clinical Scenario Repository™ (MD PnP Program), is described.

Demonstration of a medical device integration and coordination framework

This tool demonstration presents a framework for integrating and coordinating the activities of medical devices. The framework uses a publish-subscribe framework for communicating with and controlling devices and a model-driven component-based development environment for rapid implementation of device coordination tasks. A multi-faceted graphical user interface supports activities such as device/driver registering and installation, model-based development of device integrations, and monitoring system activities/performance. The framework also includes a control/display environment that clinicians would use to (a) display integrated information pulled from multiple devices and (b) launch and interact with device coordinations that automate clinical workflows. The distribution of the framework includes a collection of mock medical devices, and instructions for integrating real devices. The codebase is freely available under an open source license.

Effective standards and regulatory tools for respiratory gas monitors and pulse oximeters: the role of the engineer and clinician.

Developing safe and effective medical devices involves understanding the hazardous situations that can arise in clinical practice and implementing appropriate risk control measures. The hazardous situations may have their roots in the design or in the use of the device. Risk control measures may be engineering or clinically based. A multidisciplinary team of engineers and clinicians is needed to fully identify and assess the risks and implement and evaluate the effectiveness of the control measures. In this paper, I use three issues, calibration/accuracy, response time, and protective measures/alarms, to highlight the contributions of these groups. This important information is captured in standards and regulatory tools to control risk for respiratory gas monitors and pulse oximeters. This paper begins with a discussion of the framework of safety, explaining how voluntary standards and regulatory tools work. The discussion is followed by an examination of how engineering and clinical knowledge are used to support the assurance of safety.