Medical Device Communication: A Standardsbased Conformance Testing Approach 

John J. Garguilo1

, Sandra Martinez1, and Maria Cherkaoui1

1

National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, USA 

Abstract

NIST researchers are collaborating with medical device 

experts to facilitate the development and adoption of 

standards for medical device communications throughout 

the healthcare enterprise as well as integrating it into the 

electronic health record. We have developed test tools and 

corresponding electronic representation of an international 

standard's information model that provides several 

important capabilities leading toward device 

interoperability. We describe a conformance testing 

approach which allows users to abstractly define devices via 

device profiles and implementation conformance statements. 

This information and tooling is subsequently used to provide 

syntactic and semantic validation of medical device 

messages according to medical device communication 

standard ISO/IEEE 11073. 

Keywords: Conformance; Interoperability; Medical Device 

Communications; Testing Approach; XML; XML Schema. 

1 Introduction 

 The reality that medical devices need to communicate 

with tens, if not hundreds, of other devices of varying 

makes, models, and modalities have large market and 

substantial healthcare implications. Acute point-of-care 

settings such as a hospital's intensive care unit, a patient's 

bedside, or personal telehealth location require each class of 

medical device to use the same terminology and data 

organization to seamlessly and reliably communicate 

physiological data. Healthcare communication standards 

that address plug-and-play medical device interoperability 

are critical. 

NIST researchers are collaborating with medical device 

experts to facilitate the development and adoption of 

standards for medical device communications throughout 

the healthcare enterprise as well as integrating it into the 

electronic health record. We have developed test tools and 

corresponding electronic representation of an international 

standard's information model that provides several important 

capabilities leading toward device interoperability. 

Conformance testing is a key step leading to, although not 

guaranteeing, interoperability[1]. Conformance test 

methodologies are presented which provide the medical 

device industry with tools to ensure that critical devices 

correctly implement the medical device standards. Correct 

implementation of standards lead to plug-and-play devices 

thereby allowing clinicians to focus more on the patient and 

less on the devices. The ability to reliably and effectively 

integrate data from a broad range of point-of-care devices 

will ultimately lead to a reduction in medical errors and the 

associated loss of life. 

Central to our approach is an electronic data representation 

of the Standard’s information model and tools derived from 

that electronic representation. This approach enables 

medical devices, through tooling, to be abstractly defined 

and validation of messages exchanged between actual device 

implementations. Further, by use of this tooling, devices 

can be specialized to meet particular implementation profiles 

that address specific workflow or use cases. Defining and 

applying constraints enables more thorough conformance 

testing thus leading to greater levels of interoperability 

assurance. 

2 Medical Device Communication Standard 

The ISO/IEEE 11073 Health Informatics – Point of 

Care Medical Device Communication standard (x73) 

defines a set of information objects and functions needed 

for medical device communication. Such a standard was 

developed to address the critical need of enabling medical 

devices to share physiologic data between devices and 

computerized healthcare information systems. Two primary 

parts of this standard used in our approach pertain to the 

Domain Information Model (DIM)[2] and 

Nomenclature[3]. The DIM provides the objects and object 

relationships necessary to abstractly define a device. It 

defines the overall set of information objects as well as the 

attributes, methods, and access functions which are 

abstractions of real-world entities in the domain of medical 

devices and device communication. Nomenclature defines 

terminology and codes used across classes of medical 

devices. 

3 DIM XML Schema 

 We developed a DIM XML[4] Schema[5] (XSchema) 

which is an XML language (or metagrammar) for defining 

the syntactic structure and semantics of the XML document 

representing the x73 DIM. The XSchema supports the x73 

DIM primary requirements of providing a detailed 

specification. An XML schema was selected as the 

technology employed to enable information modeling 
capabilities while maintaining the integrity of the structure 

and vocabulary. The XSchema was created as a 

foundational component for developing the conformance 

test tools described below. The XSchema allows the use of 

information objects defined in the DIM in an automated 

fashion and is used to validate conformance claims set to 

ddress conformance requirements. 

dentified in the x73 standard include 

 definition (attributes, behaviors 

ributes/notification/behavior 

bjects, attributes, 

• Allow for future extensions of the model. 

structure and vocabulary as defined by the 

73 standard. 

ompliant described using the x73 standard’s nomenclature. 

utility as an early stage 

teroperability function. 

a

Features implemented in the XSchema to satisfy the 

requirements i

capabilities to: 

• Represent common data types, 

• Ensure DIM object

and notifications), 

• Ensure containment association, 

• Represent att

inheritance, 

• Ensure object cardinality, 

• Ensure term codes (Managed O

behaviors and notifications), and 

NIST developed a tool based on the x73 DIM using the 

XSchema to provide the capabilities necessary to assure that 

manufacturers are defining the information required by the 

x73 standard. Furthermore, vendors may adopt this public 

domain XML schema to contribute to their own 

implementation development goals. Adoption of the schema 

into a vendor implementation information model maintains 

integrity of the 

x

4 Conformance Tools 

 Our ICSGenerator tool[6][7] enables users to produce 

XML device specializations that are a form of device 

profiling. Device specializations may be constrained (to the 

value level) to address more specific conformance testing. 

The ICSGenerator tool provides users an easy to use 

interface to shape, while maintaining compliance to, the 

Standard’s information model by adding and/or removing 

objects; including the object’s attributes, behavior, and 

notifications. The abstract representation of a device is 

created by a user, validated by the tool against the 

XSchema, and saved in XML format. The resultant XML 

files therefore abstractly define a device which is x73 DIM 

c

Users attempt to provide specific details about their device 

by issuing an Implementation Conformance Statement 

(ICS). The ICS is a form of data sheet that discloses details 

of a specific implementation and specifies which features 

are provided. The ICS provides a consistent means to 

describe device features spanning manufacturers or various 

makes and models. ICSs can effectively narrow the scope of 

device interfaces by defining supported features thus leading 

to a reduction (and ultimately elimination) of the need to 

have unique interfaces for each connecting or 

communicating device. The ICSGenerator tool enables the 

user to easily produce automatically formatted ICSs that 

meet the requirements set in the conformance section of the 

x73 standard. Conformance statements, produced by device 

manufacturers and implementers, provide an effective way 

to increase the likelihood of communicating data correctly. 

Such statements, typically produced prior to actual 

communication, have 

in

Figure 1: Medical Device Conformance Test Tooling 

Process Flow

rt’) and an XML device 

specialization (or profile). 

ting 

segments (i.e., HL7 OBX-2 through OBX-7 segments). 

enerator tool) are 

alidated by our ValidatePDU tool[10]. 

Figure 1 (top left portion) shows ICSGenerator’s output of 

several produced ICS statements (‘General’, ‘Service 

Support’, and ‘Transpo

The ICSGenerator also enables users to load and compare 

(previously saved) device profiles, generate object diagrams 

(i.e., UML[8] class diagrams of the derived profile), and 

automatically generate partial HL7[9] observation repor

We developed a second tool that validates exchanged 

medical device messages encoded according to the x73 

standard. Syntax (i.e., the message structure) and low-level 

semantics (i.e., the message is within the constraints of the 

device profile produced by the ICSG

v

The ValidatePDU test tool validates basic syntax and 

structure of medical device message protocol data units 

(PDUs) being exchanged. Information format is initially 

defined using a medical device data language in an abstract 

syntax, i.e., Abstract Syntax Notation One (ASN.1[11]). 

This information is then mapped to, and interchanged 

through, a transfer syntax, e.g., basic encoding rules (BER) 

and/or medical device encoding rules (MDER), typically for 

efficiency in the form of integers. We created a library that 

provides the encode/decode services to parse and validate 

the message exchanged. The library services were 

developed allowing for decoding of MDER/BER encoded 
messages. The NIST ValidatePDU tool flags incorrect 

syntax and data type errors and produces a resultant 

validation report. 

ne if the message exchanged has 

x73-compliant structure. 

discrepancies and generates resultant 

alidation reports. 

ntic validation of x73 PDUs by the 

ValidatePDU tool. 

primary 

erability for 

t the point-of-care, 

in all health care environments. 

o ensure 

ompliance to the most recently approved version. 

further 

creasing the likelihood of interoperable solutions. 

 Domain information model (DIM) 

– XML schema format). 

 

4.1 Medical Device Message Testing Approach 

The ICSGenerator tool-generated device profile described 

above may also be used to configure devices. Configuration 

is typically performed on medical devices acting in an 

“agent” or “server” role. After association is established, 

the configuration information is propagated to medical 

devices acting in a “manager” or “client” role. General 

network sniffers are used to capture x73 encoded 

information, or messages, exchanged as PDUs. The 

application layer data is parsed out of the data stream to 

obtain APDUs (Application layer PDUs). The APDUs are 

encoded using a specific notation based on MDER and 

contain the medical device data we are interested in 

evaluating. The APDUs are input into the ValidatePDU

tool and parsed to determi

A second use of the ICSGenerator tool generated profile is 

to validate that the message being evaluated has content or 

semantics that meet attribute constraints defined by the user 

in the profile. The ValidatePDU tool highlights any syntax 

and object-level 

v

Figure 1 shows the described process flow of using the 

ICSGenerator tool generated XML device profile and 

syntactic and sema

5 Conclusions 

 Our approach of applying tools, based on an XML schema 

derived directly from the information model and 

nomenclature of the x73 standard, increases test 

comprehensiveness and quality and supports conformance 

testing leading to interoperability. Ultimately, these tools 

aid medical device manufacturers in achieving the 

goals established by the family of x73 Standards to: 

• Provide real-time plug-and-play interop

patient-connected medical devices and 

• Facilitate the efficient exchange of vital signs and 

medical device data, acquired a

In addition to the approach presented above this 

methodology also provides invaluable feedback into the 

standards developing organizations as the information model 

is applied and implemented. Addressing issues or 

discrepancies as discovered through such tooling lead to 

comprehensive and correct standards which subsequently 

may enter the marketplace more rapidly. Correcting 

discovered errors or inconsistencies in the Standards and 

tooling greatly reduce, or eliminate, the chance of errors 

being propagated throughout manufacturer implementations. 

Additionally, the tools become more complete and correct as 

issues are discovered using this approach. Furthermore, by 

simply updating the XML Schema and configuration files, 

the ICSGenerator tool stays in compliance. Saved device 

profiles (output from ICSGenerator and complying or 

validated against a prior version of the Standard [schema]) 

can be reloaded into the tool and re-evaluated t

c

Currently, within the personal health device domain, new 

normative additions to the x73 Standard are being 

proposed[12][13][14][15][16][17][18][19][20] and 

produced to address and optimize additional devices (for 

device specializations including pulse oximeter, blood 

pressure monitor, thermometer, glucose, cardiovascular and 

strength fitness, and independent living hub). The proposed 

information model in those additions can be modeled using 

our tooling - thus leading to more accurate standards prior to 

being approved and used. Thus more accurate and 

consistent implementations are made available 

in

NIST also continues to actively participate with the ongoing work of the Integrating the Healthcare Enterprise - 

Patient Care Device (IHE-PCD) domain and IEEE Personal 

Health Device working groups. This work strives to 

advance x73-based device information into HL7 observation 

messaging formats as well as enhance the tooling described 

above to meet industry conformance testing needs. The 

XSchema described has been accepted to become a 

normative part of the x73 standard (P11073-10202 – 

Standard for Health informatics – Point-of-care medical 

device communication –

 

MP’08 July 14-17, 2008, Las 

egas, Nevada, pp143-149. 

n 

8854, E-mail: stds.ipr@ieee.org, web: www.ieee.org 

int-of8854, E-mail: stds.ipr@ieee.org, web: www.ieee.org 

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