Data format standards to ease the exchange of vital signs dataIntroductionThe need to exchange physiological signal and other measurement data between computer systems has increased during the past few years as more and more measurements end up in digital form. The first exchange parties have been researchers who have needed the possibility to collect data from different laboratories to increase their sample sizes and to learn from each others' recordings. The growing use of telemedicine in such areas of medicine where digital recordings are made is based on the assumption that the receiver of the data can view and process the data. At present this is only possible between units which use the same equipment or some agreed interchange format with the necessary conversion programs to and from that format. The technical committee Health Informatics (TC251) of the European Committee for Standardisation (CEN) has the working group IV - Technology for Interoperability (WG IV) which has been working on this field preparing standards to alleviate the above problems. Vital signs data dictionaryIn co-operation with the IEEE committee, P1073 Medical Information Bus WG IV has collected and organised a relatively exhaustive list of physiological measurements which are made in intensive care units and electrophysiological laboratories, e.g. sleep laboratories. The list contains also body sites for the precise location of sensors, units of measurements, entries for physiological and environmental events and alarms. A 16-bit code has been assigned to each one of these data items and this code is intended to be used by all the devices of the measurement system. An information model has been defined with services to access the data items stored by a device that conforms to the specification. The model is applicable both in on-line and off-line information exchange. Additional definitions (e.g. handshaking in the beginning of the communication between a medical device and a departmental computer system) are, however, needed before devices can communicate in practise using this standard proposal in real time environments. WG IV and IEEE P1073 are working on the definition of these missing pieces. File exchange format for vital signsThe purpose of this standard proposal is to define a standard file exhange format which defines how the vital signs data are organised in a sequential file. This file can be stored, e.g. on a floppy disk or on a CD-ROM. The specification is so detailed that it is possible to access the data with different computer systems without additional information from the recording device manufacturer. If the specification is accepted and implemented by many manufacturers, the data interchange problem is close to a solution. In the present form of the specification a file in this format consists of different sections. A small fixed size identification section in the beginning of the file specifies the version of the format specification and whether an 8- or 16-bit character set is used in the text fields of the file. A demographic section contains information about the patient's name, birth date etc. A medical device presentation section describes the devices from which the data has been obtained. Additionally, there is an optional manufacturer specific section to which manufacturers can store proprietary information for which no data structures have been defined. An optional image section gives the possibility of storing a digital image about the electrode montage, for example. The most important section is the session archive. It contains a biosignal, numeric measurement, event, alarm and annotation data. As all sections and subsections are preceded by a tag and a field which indicates the length of the section, an application program which does not use all the data can skip the irrelevant parts. More on these topicsThe final version of the data dictionary definition has been delivered in December 1997 for approval to CEN/TC251 with the name Vital Signs Information Representation (PT5-021). After the approval the document will be made available through CEN Central Secretariat in Brussels, Belgium and European national standards bodies. Additional information can be obtained through the TC251 world wide web pages at the address http://www.centc251.org Another web page can be found at http://www.cs.tut.fi/nvarrifef.html which gives the latest information about the progress of the file exchange format specification and gives instructions how to obtain the latest draft version. The development of the format is an open process and comments and contributions are welcome. The developers of the format meet in TC251 Joint Working Group meetings which are announced in the TC251 web pages. Alpo Värri, Thomas Penzel, Gunther Hellmann, Kim Nielsen, Alberto Macerata and Christoph Zywietz Contact address: Alpo Värri Signal Processing Laboratory, Tampere University of Technology, PO Box 553, FIN-33101, Tampere, Finland Tel. +358-3-3652575; Fax. +358-3-3653857 E-mail: varri@cs.tut.fi | ||