A novel codification scheme based on the 'VITAL' and ...ekyriac/papers/Paper_J3.pdf · IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, ... This paper presents an object-oriented

IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 49, NO. 12, DECEMBER 2002 1399

A Novel Codification Scheme Based on the“VITAL” and “DICOM” Standards for

Telemedicine ApplicationsAnthoula P. Anagnostaki, Sotiris Pavlopoulos*, Member, IEEE, Efthivoulos Kyriakou, Student Member, IEEE, and

Dimitris Koutsouris, Senior Member, IEEE

Abstract—The field of interest discussed in this study is a novelcodification scheme for (vital signs) medical device communica-tion and patient monitoring data interchange, into the context ofeffective home care service provisioning. With medical technologyhaving developed in isolation and major manufacturers devel-oping their own proprietary communication protocols, whichpreclude connection to devices from different manufacturers,and with healthcare trends having evolved, pointing to primarycare, telecare and home care monitoring, there is an increasingneed for technical standardization in healthcare environmentsand the development of protocols that enable communication ina structured and open way. In this study, a novel codificationscheme has been developed, based on two healthcare informaticsstandards, the VITAL and DICOM Sup. 30, in addressing therobust interchange of waveform and medical data for a homecare application. Based on this scheme, we created a real-timefacility, consisting of a base unit and a telemedicine (mobile) unit,that enables home telemonitoring, by installing the telemedicineunit at the patient’s home while the base unit remains at thephysician’s office or hospital. The system allows the transmissionof vital biosignals (3-lead ECG, pulse rate, blood pressure andSpO2) of the patient. This paper presents an object-orienteddesign with unified modeling language (UML) of a class hierarchyfor exchanging the acquired medical data and performing alertmanagement, and investigates the applicability of the proposedscheme into a commercial patient-connected medical device, thusaddressing service and functionality requirements with focuson home-care applications. The system has been validated fortechnical performance over several telecommunication means andfor clinical validity via real patient-involved pilot trials.

Index Terms—Home care, object-oriented modeling and design,open systems, standardization, telemedicine.

I. INTRODUCTION

A. Characteristics of the Problem Domain

I N THE MAJORITY of countries there is an increasing em-phasis being placed on primary care in improving the health-

care services. Concomitant with the changing nature of health-care delivery is an expansion of demand on these services as a

Manuscript received July 24, 2001; revised July 2, 2002. This work was sup-ported by the European Commission under the Information Society Initiativefor Standardization (ISIS) Programme in the framework of the “VITAL-Home”project [46], [47].Asterisk indicates corresponding author.

A. P. Anagnostaki, E. Kyriakou, and D. Koutsouris are with the NationalTechnical University of Athens, School of Electrical and Computer Engineering,15773 Zografou, Athens, Greece (e-mail: [email protected]).

*S. Pavlopoulos is with the National Technical University of Athens, Schoolof Electrical and Computer Engineering, 15773 Zografou, Athens, Greece(e-mail: [email protected]).

Digital Object Identifier 10.1109/TBME.2002.805458

result of demographic changes, an increasing proportion of theelderly in the population and a shift in the nature of the diseaseburden. In addition, as patients have more disposable income,health, healthcare and preventative care increase in potential,whereas the increases in patient throughput and the implica-tions for health services produce demand for new initiatives.Thus, healthcare providers need to consider how to harness in-formation management and communication technologies into a“hospitals without walls” concept. Furthermore, the changes inthe European Community’s healthcare requirement has evolvedfrom being predominantly concerned with acute infectious dis-ease control to the management of chronic noninfectious dis-ease, such as cardiovascular complaints, respiratory disorders,diabetes, etc. These tend to be slow in developing, progress in-sidiously, often highly variable in their course and commonlyneed prolonged (life-long) treatment. Within this context, themanagement costs of cardiovascular and respiratory disordersare increasing as the life expectancy of the population groupsuffering from such disorders increases. There is no doubt thatas pressure increases on hospital intake there will be a greateremphasis placed on the use of home care. Success may lead tocost reduction and containment and more effective healthcaredelivery, particularly in regions of limited infrastructure or geo-graphically challenged.

Home care monitoring is in use today on a very limited basis[1], [2]. In the main part it takes the form of niche applicationssuch as simple cardiac monitoring [3], sudden infant death(SIDS) monitoring, sleep apnea studies, diabetes and respi-ratory function evaluation. These are almost all for diagnosisrather than continuous patient monitoring. Recent studies showthat [4] the number of patients being managed at home isincreasing, in an effort to cut part of the high hospitalization’scost, while trying to increase patient’s comfort. Using lowcost televideo equipment that runs over regular phone lines,providers are expanding the level while reducing the frequencyof visits to healthcare institutions [5]. In addition, a varietyof diagnostic devices give the physician the ability to see andinteract directly with the patient. Examples of such applicationsinvolve the elaboration of a wide variety of home monitoringsystems, stating in all cases the need for such efforts [6], [7].In 1996, researchers at the National Technical University ofAthens have successfully demonstrated real time transmissionof ECG data from a moving ambulance, using GSM data links[8]–[10].

0018-9294/02$17.00 © 2002 IEEE

1400 IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 49, NO. 12, DECEMBER 2002

Patient care within intensive care units and operating theaters,as well as home care that is the major application field in thisstudy, utilizes sophisticated instrumentation for the monitoring,treatment and sometimes control of therapy. An enormousamount of information, such as the medical instrumentationdata, is being generated at the point of patient care. In practice,this information is not always being captured, integrated andprocessed in order to achieve a better understanding of thepatient’s condition, although where units have integrateddevice data, improvements in patient care and cost savings havebeen identified [11], [12]. A major technical problem is thecommunication between medical devices, since manufacturershave developed their commercial devices in isolation and in away that precludes communication both between themselvesand with hospital computer and data management systems.

With medical technology having developed in the context ofrapid advances in the science of information technology andhaving incorporated these advances into the medical deviceindustry, in terms of communication interfaces the majormanufacturers have developed their own proprietary commu-nication protocols, which preclude connection to devices fromdifferent manufacturers. These nonopen, nonstandard solutionsare the current scenery in medical device communications.One problem they impose is the immense resources requiredfor development, which the manufacturer has to recoup byhigh pricing of such technology, leading into a close marketwithout competition, when the opposite tactic of open stan-dards would encourage competition, enhance effectiveness ofapplications, reduce development costs and drive down prices.Notwithstanding, open communications with their subsequentclinical, administrative and research benefits create a pressingneed for technical standardization in healthcare environmentsand the development of protocols that enable communicationin a structured and open way.

The efforts that are currently being carried out toward open,standardized communications amongst medical devices and in-formation systems include medical device directives (hardware-oriented) that are being applied through national agencies andmanufacturers. Additionally, a number of industrial health infor-matics and telematics standards (software-oriented), addressingthe communication of medical devices and information systemshave developed and evaluated in the past few years.

As far as hardware compatibility is concerned, the first steptoward standardization was initiated by the IEEE group P1073in 1984 [13]–[16], developing what has become known as themedical information bus (MIB). Numerous incarnations of thisstandard have appeared as prototypes [17], [18] but never inproduct catalogues. Hardware development is in the main partdetermined by the general product specifications of the variousdevice types, therefore several guidelines have been defined forthe development and deployment of specific types of device,such as ventilators and infusion pumps. However, although it isall very fine to have common physical network standards usedin device communications, anyone who has attempted to makeRS232 connections knows the need for specific software to in-terpret the codes and protocols. Without a structured and un-ambiguous means of representing the information, the transportand physical layer standards could achieve little.

Thus, as far as software compatibility is concerned, allmodern medical devices for patient monitoring incorporatesome form of software component, most notably in the area ofsignal processing. A few application standards have appearedthat are implemented on a voluntary basis, based on what hasbecome accepted practice or is based on “recommendation.”The American Heart Association performance recommenda-tions for the EKG namely frequency range from 0.05–100 Hzwith a time constant of 3.2 seconds is a typical example. Inaddition to the voluntary implementation of common practice,a more formal approach is applied through definitive standardssuch as the EN ISO 9703-3: 1998, “Anesthetic and Respiratorycare alarm signals—Guidance on application of alarms,”formalizing alarm coding. The most modern approach forthe medical devices software component is the developmentof standards for necessary terminology, codes, services andprotocols, based on ISO/OSI standards, which enable trueinteroperability between medical devices. The development ofthis work led to the first European standard (CEN ENV13734,commonly called VITAL) [19]. The primary work in theVITAL standard is an information model and a nomenclatureor dictionary of terms for communications of information usingcodes. This was jointly worked on with the IEEE group andincorporated into their set of IEEE 1073 standards.

B. Proposed Solution

With home care in the community increasing in necessityand importance, there is a need for novel state-of-the-art med-ical instrumentation, providing the means for fusion of remotesignal acquisition, data input and expert clinical opinion. In thisstudy, we propose a new approach for a telemedicine systemthat combines the special characteristics of a home care ap-plication with the development implications and adaptation ofopen systems. In order to meet the above different growing de-mands we created a real-time facility that consists of a base unitand a telemedicine unit that enable home telemonitoring, by in-stalling the telemedicine unit at the patient’s home while thebase unit remains at the physician’s office or hospital. This fa-cility is able to transmit 3-lead ECG, noninvasive blood pressure(NIBP), heart rate (HR), and oxygen saturation, acquired by acommercial patient monitor, over a variety of communicationmeans, based on the TCP/IP protocol [20]. The challenges wehave faced concern the incorporation in our system of the specialrequirements of home care, in terms of a patient managementscheme and a standardized process for the monitoring proce-dure, as well as the recommendations for robust, standardizeddata interchange, in terms of open communications amongstthe medical device and the information system involved in theapplication.

We propose a novel, standard codification scheme that in-corporates the structures and the management processes of theinformation exchanged amongst interoperable medical deviceand information systems. We bared into mind the special re-quirements and characteristics of home care applications, aswell as the relevant standardization efforts already available,and finally we propose a scheme that acknowledges the gaps

ANAGNOSTAKI et al.: NOVEL CODIFICATION SCHEME BASED ON “VITAL” AND “DICOM” STANDARDS 1401

Fig. 1. Object class diagram for the implementation of the medical subject.

in the various published standards and how they offer recom-mendations that are not stand-alone but rather complementaryto one another. We propose, thus, a super-set of at least twostandards that address the robust interchange of waveform andmedical data for telemedicine applications, with focus on thehome care application field, the VITAL and DICOM Supple-ment 30 standards [21]–[23]. We have formalized communica-tion management through integration of real time signal acqui-sition and processing and bi-directional data flow and we havetaken into consideration the requirement for a flexibility thatcannot only accommodate complex systems but also enablessimple low cost monitoring devices to comply without dispro-portionate cost penalties.

This paper presents the work undertaken in the frame-work of the “VITAL-HOME” project [24], funded by theEuropean Commission-Directorate General Enterprise, underthe Information Society Initiative for Standardization (ISIS)Program. The project has addressed the issues of medical datainterchange in a standardized manner and clinical managementof home-monitored patients, via the integration of VITAL ENV13 734 [19] and DICOM Supplement 30 Waveform Interchange[21]–[23] standards into a novel codification scheme based onthe two standards. A small-scale pilot application focused onassessing applicability, technical feasibility and performanceof the proposed scheme and provided the study with clinicalacceptance criteria and with validation results of integratingthis scheme into a commercial patient-connected device.

The primary intended reader of this paper is a software de-signer and/or engineer who is developing interface software formedical devices covered in the scope of the VITAL and DICOMstandards.

C. Acquaintance With the “VITAL” and “DICOM Supplement30” Standards

1) The “VITAL” Standard: The “VITAL” ENV 13 734 stan-dard is a European standard, which applies to patient-connectedmedical measurement devices that can communicate patient re-lated physiological data between devices and between a deviceand a computer system. It provides the definition of a common(device independent) representation of vital signs informationas well as the definition of a common model for accessing thisinformation. The manager/agent (client/server) framework forcommunication systems defined and used in this standard isconceptually based on the ISO basic reference model. The majorparts of this standard are:

1) domain information model (DIM);2) service model for the communicating systems and

devices;3) dictionary for information elements of the medical data

information base (MDIB) to be managed and communi-cated within the system.

The DIM is an object-oriented model that consists of objectsthat represent generalized vital signs data and relevant infor-mation, and their specialization is achieved by defining appro-priate attributes. The objects defined in the VITAL informa-tion model are considered managed (medical) objects, whichare directly available to management (access) services providedby the common medical device information service element(CMDISE), a specialization of the ISO/IEC 9595 common man-agement information service element (CMISE).

The set of objects and object instantiations occurring in anydevice of the communicating system as described in the DIM


forms the medical data information base. Each instantiationof the objects of this model needs a unique identification. Thetotal set of terms forms the medical data information base orthe “data dictionary.” Because a large number of instantiationsexist, a structured identification scheme, a nomenclature isnecessary. The nomenclature for the MDIB comprises severalthousand terms concerning the (object-oriented) modelingelements, demographic patient data, device descriptions, mea-surement values, measurement methods, alarm information,etc.

2) “DICOM Supplement 30” Standard:DICOM workinggroup 1—cardiac and vascular information, has undertaken awork task to develop this proposed DICOM Supplement to ad-dress the robust interchange of waveform and related data inDICOM. This work primarily targets cardiology waveforms, in-cluding electrocardiograph and hemodynamic signals, but WG1has endeavored to ensure it is applicable to a broad range ofwaveforms when acquired in a medical imaging environment,although waveform interchange in other clinical contexts mayuse different protocols more appropriate to those environments.For example, HL7 may be used for transfer of waveform obser-vations to general clinical information systems, and IEEE MIBmay be used for real-time physiological monitoring and therapy.

As a Supplement to the DICOM Standard, this proposal relieson the standard DICOM services for information interchangein an imaging environment. It provides a rudimentary mecha-nism to interchange waveform data, the Curve Information En-tity within the Standalone Curve Information Object and withinother composite image objects.

II. M ETHODOLOGY

A. Introduction

Our work focused on the design, modeling and developmentof interface and communication software for a medical monitorallowing for the collection and transmission of diagnosticallyimportant biosignals (ECG, blood pressure, oximetry, etc.), aswell as the integration of a telemedicine pilot system, which im-plemented the coherent transmission and archiving of the med-ical data at a remote consultation center. The proposed systemdeals with an open-systems architecture that achieves to trans-late the monitoring medical information and its managementprocesses into information object models, based on the combi-nation of the VITAL and DICOM standards.

The methodology followed in order to achieve the abovegoals included three major phases: In the first phase, the userrequirements were determined followed by the system andservices description, providing the system architecture andfunctional characteristics. In the second phase, the integrationof the standards has been modeled in compliance with theobject-oriented software engineering concepts, in order torealize a class hierarchy for the medical data interchange andthe technical and physiological alert and data management, inaccordance with the standards under study. In the third phase,finally, software and hardware specs as well as functionalrequirements have been addressed and implemented into atypical telemedicine system, the information model of whichwas a novel codification scheme based on the two standards.

Fig. 2. Object class diagram for the implementation of the alert subject.

The overall system was verified accordingly with a protocol ofprocedures, in order to ensure a standard level of practice.

B. From Requirements of Home-Care Into StandardizedPatient and Data Management

In translating the special characteristics of a home-care ap-plication into a standardized codification scheme for medicaldevice interface, data, patient and alarm management, we haveconsulted the CEN “interoperability of patient connected med-ical devices” draft (ENV13735) [25]. This draft describes dif-ferent medical device types and correlates them with applica-tion scenarios and application profiles, standard and/or optional.The same devices may be used in different scenarios, which ofcourse may influence the needs for application profiles and op-tional application packages as well. We propose a scenario andapplication profile as well as a specific device type involved ina home monitoring situation, namely a patient-connected mon-itor. The type of medical device that applies to a home careapplication is not explicitly defined in any of the available rele-vant standards; rather the various hardware and software mod-ules that it is comprised of are described independently in theCEN draft. We have combined into one type the following typesof medical devices.

Configurable Patient Monitor—a patient monitoring device,configurable to patients needs by inserting different physiolog-ical measurement modules.

EKG-Machine—a device for polygraphic measurement ofpatient’s electrical activity of the heart. It delivers waveformsand also processes EKG and delivers measured parameters andinterpretation (diagnostic findings).

Pulse Oxymeter—a device for noninvasive measurement ofsaturation of hemoglobin by oxygen (SpO) in arterial blood.

NIBP Monitor—a device automatically measuring bloodpressure of the patient by an inflating cuff.

We propose a codification scheme that incorporates thespecial requirements and characteristics of the followingapplication scenario: Real time data display—patient alarmmonitoring—remote control—and interoperability. In a homecare application, the manager device not only acquires andstores data but also displays discrete and graphic parameter


Fig. 3. Object class diagram for the implementation of the archival and patient subject.

data, therefore “real-time” issues have to be addressed. Therequirement for patient monitoring capabilities is also incor-porated in our proposed codification scheme, providing thegeneration and report of patient-related alarm information,whereas the proposed scenario also includes a requirement foralarm set-point information. An additional requirement is thatthe manager can also accomplish remote control operationson a target medical device, provided that the device supportsremote control—for some legacy devices may not. With thisrequirement, the application is allowed to modify the set-pointson the medical device. This includes alarm limits (high andlow), ECG Lead selection and waveform filtering, for example.This requirement though must fulfill a higher level of reliability,therefore it includes the needs for comprehensive messagevalidation, data verification, message retries, and notificationof communication system failures. Therefore, the proposedcodification scheme supports a mechanism to send control datato the data agent and acknowledge its receipt.

The special requirements of home care have been taken intoconsideration in designing the proposed codification scheme:In the home care environment, standardized interfacing andplug-and-play operation is a necessity. In most applications, itis necessary to communicate between a bedside patient-con-nected device and remote systems. In some cases, this involvescommunication over a variety of different types of hospitallocal area networks (LANs). In other instances, this willinvolve data transmission over telecommunications systemsor the Internet. Also, a standardized communication methodfor bedside devices must provide the capability to interfaceboth “legacy” devices—i.e., devices with “prestandardized”proprietary interfaces—as well as devices with embeddedstandardized interfaces. Especially for interfacing devices withproprietary RS-232 ports, in order to enable plug-and-playoperation, it is necessary to implement protocol converters tointerface between the device RS-232 ports, and a standardizedplug-and-play interface.

The scope of the codification scheme we propose is as faras possible to satisfy the requirements detailed above, whichrefer to application or upper layer requirements only. It doesso by standardizing the messages that are transmitted betweendevices and by utilizing encoding schemes that satisfy as manyof the above requirements as is practicable and feasible on awide range of medical devices. Optional packages definingadditional capabilities have also been incorporated in ourcodification scheme. For example, technical realizations forhome care applications require controlling a modem for directconnection to the remote telemedicine center over telephoneline, or supporting Internet access. Although, in general, upperlayers should be independent from transport and lower layers,for dialing and connection several items must be configured,thus, aspects like modem control, lower layer protocols andconfiguration of the dial up process need software support andare therefore incorporated in the proposed codification scheme.

As a result of the above described requirements analysis forthe design of our codification scheme, we have identified thecommon physiological parameters and the associated depen-dent variables that may be used in a home telemonitoring situa-tion. The proposed scheme supports the concomitant transmis-sion of a number of core features and clinical components, likevital signs and dependant variables—ECG 3 leads, SpO, pulse,blood pressure—as well as physiological and technical alarm in-formation. It also enables the adjusting from a remote locationof the settings of the home-monitoring end. The above comprisethe “medical device interface” module of the proposed codifi-cation scheme. Another module is the “Archiving” module thatenables to record the full patient history as well as demographicdata and information concerning attendant doctors and relativesinvolved in the home monitoring sessions. All signals and rel-ative data are stored in a medical record, for medical and legalpurposes. Finally, a bidirectional communication protocol is re-quired to facilitate expedient handling and transfer of data be-tween the base station and the remote location, providing the


Fig. 4. Object class diagram for the implementation of the overall model.

proposed codification scheme with its third module, “commu-nications” module.

C. Medical Device Interface Module of the ProposedCodification Scheme

The proposed codification scheme for interfacing the vitalsigns monitor in our application—and for any relative “legacy”medical devices—did not aim to prototype a full-stack devicecommunications system, but rather focused on providing a stan-dardized Upper Layers Definition according to the VITAL andDICOM standards. Therefore, it depends on common industrycommunication protocols for the lower layers and off-the-shelfstandard technologies. Thus, the standardized communicationstack requires no device hardware modifications whereas theamount of memory required for the communications stack isavailable within the constraints of typical legacy devices.

1) Design Approach for the Upper Layer Software Com-ponent: The upper layers software for the device interface isbased on the VITAL DIM. We propose a codification schemethat models the device involved in a home care applicationas a hydra medical device system (MDS), which containsthree virtual medical devices (VMDs): the ECG VMD, theNIBP VMD, and the SpOVMD, which represent the medicalinformation that the application wishes to acquire and monitor.The proposed model references also the IEEE 1073 series ofstandards [26], namely the IEEE Medical Device Communica-tions—Medical Device Data Language (MDDL)—Specialized1073.1.x standards [27]–[29].

Furthermore, we propose the organization of the interfacesoftware into software packages, in accordance with the ob-ject-oriented concept, as well as the information model conceptof the VITAL standard. Specifically, we propose an informa-tion model that includes all the static attributes of the medicaldata, waveform or nonwaveform, into a medical subject (soft-ware package) and its related objects, the system-specific in-formation into a system subject, the alert management and re-porting of the medical data dynamic attributes into an alert andan extended services subject, the patient-related and data man-agement information at the remote consultation station into apatient and an archival subject, the remote control services ofthe medical device into a control subject and the communica-tion-related information into a communication subject. Overall,48 objects were necessary for our upper layers software compo-nent, in order to implement the interface with the patient monitorand to communicate the acquired medical information over thetelemedicine link.

2) Software Design and Modeling:Although the VITALstandard that we use for the Interface module of the proposedcodification scheme is described by the Coad and Yourdonobject-oriented notation, we utilized the concepts of the unifiedmodeling language (UML) [30] for the analysis and design ofthe upper layers software component. TheUML is a languagefor expressing the constructs and relationships of complexsystems, which will be developed in an object-oriented manner[31]. The UML notation is being supported by rapid applicationdevelopment (RAD) tools, like the “Rational Rose” tool forreal-time applications [32], developed by the Rational SoftwareCompany.


A UML model provided the class hierarchy for modelingthe medical device interface module for our proposed codi-fication scheme. Figs. 1–3 illustrate a selection of the UMLobject class diagrams, which show the implementation of thesubjects—software packages for our home care application,whereas Fig. 4 illustrates the object class diagram for the im-plementation of the overall model. These diagrams have beenadapted from a Rational ROSE’98 model. Some mandatoryattributes and operations are shown.

As illustrated in the above UML diagrams, for the interfacewith a patient monitoring device that is typically involved ina home care application, we propose a containment hierarchyof the upper layers software element that defines a MDSobject, containing three virtual medical device (VMD) ob-jects: the ECG VMD, the NIBP VMD and the SpOVMD.Browsing down the hierarchy, the ECG VMD contains twochannel objects, one representing the HR numeric metric, theHR status enumeration, and the HR alarm limits (high andlow) enumerations, and one representing the ECG real-timewaveform real time sample array metric, the ECG statusenumeration, the lead number enumeration and the neonateenumeration (namely the attributes defining whether themeasurement was performed on an adult or a neonate). TheNIBP VMD contains one channel representing the NIBPnumeric metric, the NIBP VMD object contains one channelobject, which represents the (compound: diastolic, systolic,and mean) NIBP numeric metric, the age, status and targetenumerations and, finally, the alarm limits (high and low)enumerations. The age enumeration defines the time stampwhen the determination of the NIBP measurement in questiontook place. The SpO VMD object contains two channelobjects, one representing the pulse rate (PR) numeric metricand one representing the SpOnumeric metric, the Qualityand status enumerations and, finally, the alarm limits (highand low) enumerations.

Finally, we propose that medical device interface softwarealso contains a service and control object, representing the re-mote control operations of selecting the ECG lead (lead I, II, orIII) and setting limit alerts. The alert status object supervises thealert condition of the monitoring device, both physiological andtechnical, whereas Archival and patient demographics are re-sponsible for patient information and archival capabilities. Themodel also contains a set of scanners, which facilitate a set ofextended (medical) object management services. Specifically, acontext scanner to exchange the medical device’s containmenttree (“c-tree”), a periodic configurable scanner (and fast peri-odic configurable scanner) to exchange numeric and real-timesample array observations, and an alert scanner to exchangemedical and technical alerts as derived by the alert status ob-ject. Finally, the communication controller is responsible forthe medical device and network connection (communication)issues.

D. Communication Module of the Proposed CodificationScheme

For the issues of communication and interconnectionamongst medical devices and information systems, into thecontext of a home care application, we recommend the widely

used TCP/IP communication protocol. The VITAL standardaddresses interoperability issues (communication) in relevancewith the IEEE documents (which mainly implement theOSI communication stack), therefore, the association controlservice element—ACSE, which is used by the OSI stackand augments the presentation layer service with associationestablishment and termination services, is being implementedin the codification scheme that we propose. On the other hand,the information management protocol, providing the servicesthat access the objects in our application is the commonmanagement information protocol over TCP/IP—ISO CMOT,identified and specialized as common management deviceinformation service element (CMDISE).

The above communication protocols have been incorporatedinto the proposed codification scheme, by adopting a cannedprotocol data unit (PDU) approach, for the PDUs that are in-terchanged amongst the communicating parties involved in theapplication; the medical device at the home-based end and theinformation system at the remote consultation end. In the pro-posed codification scheme, we have specified the PDUs in com-plete encoded form and, therefore, instead of creating parsingsoftware that is fully knowledgeable of PDU structure, a designgoal was to rely on “canned” PDU definitions or templates andto rely also on fixed offsets as much as possible, the assump-tion being that this would result in simpler implementations thatrequire fewer system resources (e.g., CPU bandwidth and pro-gram memory). In addition to that, the native communicationprotocol software used by the vital signs monitor for externalcommunication has been left active and operational.

Furthermore, while transmitting the data structures of theupper layer software component, we have come across the needfor an abstract syntax and the corresponding transfer syntax(encoding rules) that specify the representation for the datatypes defined in the abstract syntax. The use of the abstractsyntax in a communicating systems application is to separatethe data types as they appear in the application protocol fromhow they physically appear in the application. On the otherhand, the task of the transfer syntax is to represent unambigu-ously the values of the data types as they are transmitted on thenetwork. We propose that the static data structures of the upperlayer software component are encoded to sequential binarystrings, which finally appear on the network. We performedagain a preparsed encoding that is based on the ISO 8824—ab-stract syntax notation one (ASN.1) and the ISO 8825—basicencoding rules (BER), as defined in the CEN/TC 251/PT35Interoperability Document [25], which references the VITALstandard. As already mentioned in a previous paragraph, thePDUs of the communicating software of our application wereimplemented in complete encoded form (fixed offsets), insteadof creating parsing software fully knowledgeable of the PDUstructures, a design tradeoff for reasons of system resourcessaving.

E. Archiving Module of the Proposed Codification Scheme

In our home care application, both the system’s home-basedstation and the remote consultation station are equipped witharchiving databases. The local database module provides


Fig. 5. System database information model.

storage facilities for the data transmitted over the telecommuni-cation network. While data collection from the medical devicesis active, all data captured is stored in the database. In case oflink loss, the medical data is available for transmission later,when such request is made.

The Archiving module of the proposed codification schemeis based on the DICOM Supplement 30 recommendation. Wepropose a codification scheme that stores the acquired and trans-mitted medical data at the remote consultation center in a data-base that is implemented according to a DICOM InformationModel. More specifically, the archiving functionality of our ap-plication is based on the DICOM Supplement 30.0 standard anddefines an information model for storage of medical data (sig-nals and patient information). We propose the use of the entitiespatient, study, study components and results: The patient en-tity contains the characteristics of a person for whom medicaldata are transmitted and stored with the proposed system. Thestudy entity is a collection of one or more study’s components.Each study is associated with exactly one patient and leads to thestudy results. The study component is used for grouping signalsentities. Each study component is associated with exactly oneequipment and with exactly one study. A signal is related to asingle study component within a single study.

This DICOM information model is mapped to a relationaldatabase, which stores the relevant information of the moni-toring session data and results. Fig. 5 illustrates the entity-re-

lation diagram of the database information, which defines thestructure and organization of the archived vital signs and med-ical information. The notation is in accordance with the DICOMinformation model.

III. A PPLICATION DESCRIPTION

A. System Architecture

The final developed system is a combination portable/wear-able setup that allows for the collection and transmission ofdiagnostically important biosignals (ECG, blood pressure,oximetry, etc.) [33]. It is architecturally divided into twodifferent operational sub-systems. The first one serves thetasks of acquiring and encoding the vital signs and is locatedat the patient’s home. The second subsystem collects, througha communication link, the vital signs in order to decode,monitor, process and store them. This is located at the remoteconsultation center, where also the medical experts are located,providing the “monitoring service.” During the monitoringsession, the signals being captured by the biosignal monitorare observed by both parties in real time mode. In order for theconsultation center to keep track of the patient data received, itis equipped with an archive of all relevant patient information(biosignals, patient data, study data, etc.). In general, the systemfunctionality consists of the following main elements:


Fig. 6. Architecture of the pilot system.

1) acquisition home-based station including the medicalmonitoring device, the encoder/decoder and the commu-nication module;

2) healthcare center viewing station including the en-coder/decoder, the viewing station with telecommandoptions and the communication module.

The acquisition home-based station involves a standard com-mercial medical device, a portable vital signs monitor (PVSM)that performs the vital signs acquisition and display, namelythe Johnson & Johnson CRITIKON DINAMAP PLUS Mon-itor 8700/9700 [34]. Its functionality is to acquire the vital signsdata, through the monitoring device’s RS-232 serial port, andto communicate it to the Encoder/Decoder that implements thecodification scheme that this study describes. The home-basedacquisition station has been hosted in an industrial portable per-sonal computer (PC) equipped with a digital modem, respon-sible for the physical communication layer.

At the remote consultation site there is a central server thatcollects, decodes, monitors and stores vital signs transmittedby the patients’ locations [35]. In terms of the communicationequipment, the infrastructure is similar to that described for thepatient’s home above. The configuration of the consultation sta-tion is a Windows 98 Intel based PC, operating at the involvedcare provider sites, and supporting data storage. The consulta-tion center server is also connected to the Internet in order tohave the capability of electronic communication (e.g., electronicmails, etc.), in addition to the monitoring functionality. Fig. 6 il-lustrates the architecture of the pilot system.

B. User Interface

The VITAL-Home acquisition station uses a windows-typegraphical user interface (GUI) [36]. This type of interface was

selected, as it requires not much user input and furthermorenecessitate not much additional user training. The consultationcenter monitoring station also uses a windows-type graphicaluser interface. Selection of actions is being done by suitablepointing device (a mouse) without, under any circumstances,requiring excessive user input. The system displays continuousECG, SpO (hemoglobin oxygen saturation), NIBP, andHR–PR in waveform and numeric format in real time. Morespecifically: The system displays and measures ECG wave-forms in three leads, namely lead I, II, and III, one lead at a time.The ECG can be displayed on a per-lead basis in three differentspeeds, 12.5 mm/s, 25 mm/s, and 50 mm/s. The system allowsfor the display of a frozen/paused ECG waveform, which can berewound and forwarded. PR is displayed in a numeric format.When displaying the ECG waveform, the system displays inalphanumeric form the following information: lead used, speed,and scale.

In regards with numeric medical data, the system hardwarehas the means to measure the hemoglobin oxygen saturationin the blood stream. In the absence of any other PR measure-ment, the system acquires a waveform resulting from the SpOmeasurements. The PR is being computed from such measure-ments and shown in numeric form. Also, the system has themeans to measure in a noninvasive manner the systolic, dias-tolic and mean-arterial pressure. The system is able to take mea-surement of the latter pressures in an automatic fashion withoutoperator intervention. The NIBP is being shown in numericformat. Finally, the system provides physiological as well astechnical alarms in visual forms. Regarding the physiologicalalarms, low and upper limits alarms are being defined for all nu-meric parameters that are shown on the display monitor. Specif-ically: PR high, PR low, SpOhigh, SpO low, NIBP diastolic


high, NIBP diastolic low, NIBP systolic high, NIBP systoliclow, NIBP mean high, and NIBP mean low. Regarding Tech-nical alarms, a few procedural and hardware technical alarmsare being defined, namely ECG lead fail, NIBP procedural andPulse oximeter procedural. The system displays the status of thetelecommunication link connection at all times. When link lossis imminent, the system displays an alarm, whereas display ofinformation concerning the link status is simple and straightfor-ward.

C. Communications and Software Development Environment

Transmission is possible over different telecommunicationlinks [37], for it is based on the TCP/IP protocol, a well-definedpacket-oriented protocol, providing error detection and recoverywith possible retransmission of erroneous packets. Since thephysical layer is an RS-232 serial line, traditionally used in thetransmission through telephone lines, together with modems,the link layer has been developed by a specialized protocol, thepoint to point Protocol (PPP) [38]. The selection of the PPPprovided us support for the TCP and IP header compression,reducing the overhead added to the data to be transmitted aswell as link control, in order to establish, configure and testthe data-link connection. The design goal has been to developan automatic connection procedure, in order to reduce as muchas possible the connection time and to avoid human operationduring this phase.

The overall application has been integrated with the BorlandDelphi 4.0 environment, an object-oriented, visual-program-ming environment for rapid application development [39], [40].

D. Standards Validation—System Verification

In order to address the validation and clinical acceptance is-sues of our application, pilots were set-up between home-mon-itoring stations and a telemedicine consultation center. The pi-lots focused in assessing applicability, technical feasibility andperformance of the proposed codification scheme based on thetwo standards. Within the availability of technical, financial andhuman resources and under the constraint of the time-schedulenumerous monitoring sessions were performed in order to pro-vide an adequate internal validity for the study. Four types ofheart disease were considered in the pilot trials: coronary insuf-ficiency, hypertentional heart disease, arrhythmia, and postsur-gical patient after bypass operation.

During demonstration, participating medical personnel haveevaluated the system in terms of functionality and usability. Inorder to be able to draw retrospectively meaningful conclusionsand useful feedback, a brief practical and easy to fill in datacollection sheet (DCS) has been designed and used for everyinvestigated person, in order to record data concerning crucialinformation needed for the demonstration. In the end of the ex-periment, every doctor involved has filled out a questionnaire,based on predefined quality requirements, which allowed forretrospective evaluation and analysis. The DCS was designedaccording to the common industry format (CIF) for usabilitytest reports [41], [42]. The involved in the pilot demonstrationstaff has been using the system for 40 working days, for a min-imum 15 min up to maximum 25 min/day, for a period of almostsix months.

Fig. 7. Graphical representation of the duration of PR interruptions versus thesession’s ID number.

IV. RESULTS

In the pilot project, we adapted a CRITICON DINAMAPvital signs monitor, a proprietary monitoring software (Win-dows 98-based) and a PC located at the remote consultationcenter and we demonstrated their bi-directional intercommu-nication, based on the proposed codification scheme, whichresulted from the integration of the VITAL and DICOMSupplement 30 standards. We have isolated an applicationscenario, namely a patient monitoring situation that involvesalarm handling in the home care domain and we identifiedthe special characteristics and requirements of such scenario.Consequently, we have incorporated these requirements intothe proposed codification scheme, keeping it in compliancewith the two standards. Finally, we have tested and validatedthis scheme via its integration into the upper layers softwarecomponent that implements the interface with the medicaldevice, as well as the communication and archiving of medicaldata in a home telemonitoring case. The telemedicine systemthat was modeled according to the proposed codificationscheme has been verified and tested also for technical and clin-ical functionality, effectiveness and fulfillment of the identifiedspecial characteristics involved in home care applications.

In terms of technical issues, demonstration activities con-centrated on verifying compliance to user functional and tech-nical specifications and assessment of system performance. Theresults showed the stability and robustness of the system inreal-life medical situations. More specifically, the system per-formed a sufficient control on the medical device and managedto prove the following:

1) rigorous error recovery;2) physiological and technical alarm handling;3) remote control capabilities (ECG lead change, NIBP ini-

tialization of procedure) were always possible;4) reliability and stability of the PSTN dial-up connection

was proven. No communication failures and very raretransmission interruptions were observed;

5) received biosignals were undistorted and of interpretablequality.

In the following graph (Fig. 7), we illustrate the time stops forPR transmissions per session, as well as the transmission stoptime, indicatively for 40 monitoring sessions.


In terms of clinical issues, pilots have demonstrated theperceived potential advantages from the system, pointing outan increase of the availability of possibly critical information,thereby improving the care provided to the patient and ex-tending the value of telepresence. Amongst potential benefitsare increased patient survival rates, faster theater preparationand earlier requests for staff/equipment in emergency situationsand fewer inappropriate prehospital procedures. It rendersreduction of average length of hospital stay, strengthens thepatient confidence and provides support to patient’s relatives.The potential use of the system in rural areas, far from spe-cialized healthcare institutions, as well as its use by elderly orpersons with disabilities will enable the uniformity of healthcare provision within countries and throughout Europe; thusproviding better opportunity for citizens to participate in allaspects of economic and social life. Healthcare delivery couldbecome more effective, particularly in the regions that havelimited infrastructure or are geographically challenged.

As far as the validation of the two standards is concerned,cross comparison between the two standards has led to therealization that they carry many differences as far as theirinformation and service models as well as coding schemesare concerned. Moreover, the DICOM standard does not havehardcore object-oriented design. Even though it uses O–Oterminology, closer examination reveals that the design followsa classic structured approach. Although this approach doesprovide data modularity, it lacks the behavioral inheritance andabstraction, which are essential to the object-oriented model.

Thus, combination of the two standards at the level of objectdefinition has proven a difficult task. We concentrated on pro-viding a novel codification scheme based on both standards, thatpointing out the features of the standards that best address dif-ferent aspects of a telemedicine (home care) application. There-fore, the VITAL standard has been used for interfacing with thedevice, modeling the vital signs and medical information, re-motely controlling the medical device and monitoring the phys-iological and technical alerts. On the other hand, the DICOMstandard has been evaluated best suitable for archiving that spe-cific subset of vital signs and patient related information, whichis necessary to be kept from the monitoring sessions.

As far as the pros and cons of the codification scheme wepropose are concerned, we see that combining the two standardsextends the performance of existing monitoring devices. The in-tention is to achieve this through an add-on encoder/decoder thatenables compatibility between diverse instruments in a telemon-itoring context. It is also concerned with defining an approachthat can be integrated into new product design for such appli-cations as stand alone telemonitoring systems. It is importantin establishing a common approach to medical device integra-tion with open systems thus increasing flexibility and portabilityfrom hospital to home care.

We propose a codification scheme for standardized medicaldevice communication and home monitoring management byidentifying those who can be classified as users of standards, de-vices and systems for home monitoring. It was not the purposeof our work to generate a standard for vital signs monitoring inthe home. This is the task of “standard authorities” and appro-priate committees assigned to create formal approaches to care.

However, standard authorities may evaluate the outcome of thiswork and implement procedure at local, national and regionallevels if appropriate. From a standardization point of view, theproposed scheme contributes directly to life cycle extension andconsequently is a factor in cost reduction. Conformance to stan-dards can reduce the risk of situation noncompliance as well asthe reduction of the risk of system obsolescence. In many casesstandards represent the most stable technology interfaces. Thesehave high levels of support, often continuous, as technologyevolves into upwardly compatible products. The developmentof the proposed codification scheme compliments existing stan-dards and serves to demonstrate that the extension of existingproduct design and system life cycles is possible. Additionally,it can provide input to new products incorporating subsequentgenerations of the software integrated with front-end hardwareand application software for achieving to provide an effective,transportable remote monitoring system.

V. DISCUSSION

The developed system is thought to be a rudimentary proto-type that can lead the course of the future telemedicine practice,via the recommendation of telemonitoring applications, ad-herent to relevant European and international standards. Furtherexploitation of the interconnectivity of this system with otherstandards-compliant systems will strengthen its applicabilityinto a future environment of interoperability. The system’smodular design supports the addendum of telemetry and dataprocessing services and other standards-compliant function-ality, like the healthcare multimedia reports (HCMR) [43] andfile exchange format (FEF) [44], as well as the upgrade ofthe technology used. Specifically, the proposed system wouldenhance its applicability with the integration of a standard formapping its object model to a linear memory model for filestorage. Such a standard is indicated in the interim report of theproject team CEN/TC251/PT-40, namely the “File ExchangeFormat for Vital Signs” (Revision 1.0, 29/11/1999).

The proposed codification scheme could also benefit signif-icantly from the integration of a standard that addresses the in-terconnection of medical devices, although already significantparts of this scheme has been taken into consideration. Thisstandard is ENV 13 735 Health Informatics—Interoperability ofPatient-Connected Medical Devices [25], prepared under the di-rection of the European Committee for Standardization (CEN).

Finally, it is encouraging to note that as a result of the cooper-ation of CEN and IEEE, a new family of standards for providinginterconnection and interoperability of medical devices andcomputerized healthcare information systems is rapidlyemerging. It is firmly based on international standards foropen systems communications and on the base layer standardsand standardized profiles for the actual protocols and servicesspecified. It will be entitled Health informatics—Point-of-caredevices—detail [45].

Finally, toward other information structures, it seems that theidea of a common data architecture, vendor-neutral and plat-form-independent—as seeked for by the VITAL and DICOMstandards,—points directly to the World Wide Web Consortium


(W3C) standard, Extensible Markup Language (XML). It is be-lieved that XML can provide a means to share and communicatein standardized and effective manner clinical information, and,therefore, seems to be the obvious continuation of the work de-scribed in this paper. Already the CEN TC251 Working Groupshave expressed strong interest in the XML potential for the im-plementation of health informatics standards.

ACKNOWLEDGMENT

The authors would like to thank all the project participantsfor their significant contribution and fruitful collaboration.

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Anthoula P. Anagnostakireceived the University degree in electrical and com-puter engineering and the Ph.D. diploma in health telematics from the NationalTechnical University of Athens, Athens, Greece, in 1996 and 2001, respectively.

From 1996 to 2000, she was a Project Manager and Researcher at the Instituteof Communication and Computer Systems of the National Technical Univer-sity of Athens, leading several European and national research and developmentprojects. In 2000, she joined the OTE Hellenic Telecommunications Organiza-tion S.A. as Project Manager in the investment of Operation Support Systemsfor end-to-end service provisioning of new generation data networks. The areaof her research interest includes standardization of interfacing with medical de-vices, telemedicine, medical informatics, and telematics.

Sotiris Pavlopoulos(S’88–M’91) was born in Athens, Greece, in 1965. He re-ceived the degree in electrical engineering from the University of Patras, Patras,Greece, in 1987 and the M.Sc. and Ph.D. degrees in biomedical engineeringfrom Rutgers University, New Brunswick, NJ, in 1990 and 1992, respectively.

From 1992 to 1995, he was a Postdoctoral Fellow at the National TechnicalUniversity of Athens. He is currently a research Associate Professor at theInstitute of Communication and Computer Systems, the National TechnicalUniversity of Athens. He has been active in a number of European researchand development programs in the field of telematics applications in healthcareand has been the Principal Investigator in several European and Nationalresearch programs. His current research interests include medical informatics,telemedicine, image and signal processing applied to biomedicine, ECG,ultrasound imaging, and tomography.

Efthivoulos Kyriacou (S’97) was born in Paphos, Cyprus, in 1972. He receivedthe diploma in electrical and computer engineering from the National TechnicalUniversity of Athens (NTUA), Athens, Greece, in 1996 and the Ph.D.degree inbiomedical engineering from the Department of Electrical and Computer Engi-neering, NTUA, in 2000.

From 1996 to 2000, he was a Research Postgraduate Student at theInstitute of Communication and Computer Systems, NTUA, working inthe area of biomedical engineering in several EU funded research projects(AMBULANCE, MOMEDA, EMERGENCY-112) concerning telemedicine,medical imaging, and medical informatics. From 2000 to 2001, he workedwith the Athens Medical Center Group, Athens, in the fields of telemedicineand medical databases. Since November 2001, he has been working as aPostdoctoral Researcher at the Cyprus Institute of Neurology and Genetics inthe fields of medical image processing and medical informatics. During 2002,he was involved in EU funded research projects concerning telemedicine andmedical data (TELEPLAN, D-LAB). He has published several journal andconference papers in the fields of telemedicine, medical imaging, and medicalinformatics.

Dr. Kyriacou is a member of the IEEE Engineering in Medicine and BiologySociety (EMBS), IEEE Computer Society, and the Hellenic Society of Biomed-ical Engineering.

Dimitris Koutsouris (M’96–SM’98) was born in Serres, Greece, in 1955. Hereceived the diploma in electrical engineering from the Technical Universityof Patras, Patras, Greece, in 1978, the DEA in biomechanics from the ReneDescartes University, Paris, France, in 1979, the Ph.D. degree in genie biologiemedicale from the University of Paris XIII, Paris, France, and the Doctorat d’Etat in biomedical engineering from the University of Paris V, Paris, France, in1984.

Since 1986, he has been a Research Associate with the University of SouthernCalifornia in Los Angeles, and the Renè Dèscartes in Paris, France. Currently,he is a Professor of biomedical engineering and the Chairman of the Departmentof Electrical and Computer Engineering at the National Technical University ofAthens, Athens, Greece. He has published over 100 research articles and bookchapters and more than 150 conference communications.

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