Open Communication Standard for Medical Equipment

Modern medicine, especially intensive care medicine, requires equipment that automatically interacts to monitor and treat patients. Because various manufacturer equipment relies on different interfaces and transmission protocols, this communication is often not possible.

One way to address this issue is through open system architectures and standardized communication protocols. One of the first results of these efforts is the ENV 13734/35 suite of CEN standards, also known as “VITAL“, an acronym for “Vital Signs Information Representation“, the description used by the “European Standards“ project.

The Fraunhofer Institute for Integrated Circuits IIS has been helping to advance the development and implementation of this standard at the national (DIN) and global (ISO 11073) level for several years.

In describing the equipment- and manufacturer-independent representation and transmission of vital signs, VITAL defines a high-level communication model that allows access to the data. A key element here is the real-time transmission of the vital parameters, as well as automatic configuration and synchronization of the interconnected equipment.

The potential fields of application include capturing biosignals from individual diagnostic equipment and displaying the corresponding curves in real-time on remote monitors (intensive care stations), sleep laboratories, heart catheter measurement instruments or even the simultaneous capture, monitoring and case-by-case display of a range of biosignals from multiple patients across a network.

The “VITAL“ communication architecture is based on the ISO management system “agent/manager“-concept. It defines the application layer in the ISO/OSI layer model, thus  guaranteeing the flexibility to select the underlying transport protocol. This allows “VITAL“ to be used with Bluetooth, TCP/IP, IrDA or other transmission systems.

The automated ad hoc equipment communication feature requires that all communicated information elements be clearly implemented in corresponding codes. To do this “VITAL“ relies on an object-oriented information model.

A “medical data information base“ (“MDIB“) on both the agent and manager side of the system contains application-specific object and attribute instances that are defined in the model. In an extensive nomenclature, unique codes were defined for all of the model elements, equipment types, dimensions, measurements, medical measurement values and conditions used in the “MDIB“. In order to clearly denote these codes for developers and users, a special “systematic name“ was introduced that permits distinct semantic correlation across disciplinary and linguistic borders.

The middle figure depicts an example of the “VITAL“-specific modeling of medical equipment. In this case the model displays thermometer and blood pressure watch values, plus patient-specific data, in a corresponding object hierarchy and then creates an overall system.

Using plug-and-play, any combination of “VITAL“-compatible equipment can be transformed into an interoperable unit. In order to satisfy the wide range of application requirements, from intensive care to home care, the highly-scalable “VITAL“ standard can be implemented with a simple, low-resource “polling mode profile“ or for maximum flexibility with a “base line profile“. “VITAL“ basically establishes the underlying communication behavior, leaving the actual implementation and application design up the programmer. For the information modeling of commonly-used equipment or functions, such as an EKG, corresponding “device profile“ standards help ensure interoperability.