Search

Henkilökohtaisen terveyden seuranta kasvattaa nopeasti suosiotaan. Laitteiden yhteentoimivuus on merkittävässä roolissa henkilökohtaisen terveyden seurannassa. Laiteliitynnät muodostavat perustan yhteentoimivuudelle. Standardoidut laiteliitynnät pyrkivät vähintään syntaktiseen yhteentoimivuuteen. Tässä artikkelissa selvitetään henkilökohtaisen terveyden seurantaan liittyviä laiteliityntästandardeja ja niiden käyttöä edistäviä organisaatioita. ISO/IEEE 11073 on merkittävin terveystekniikan laiteliityntästandardi joka on saanut taakseen kolmen merkittävän yleiskäyttöisen liityntästandardin, Bluetooth, USB, ja Zigbee, tuen. Sen merkittävin haastaja on IP‐tekniikan yleistyminen ja IP:n päälle kehitetyt yhteentoimivuusstandardit. Artikkelissa käydään lisäksi läpi standardeja kehittäviä organisaatioita ja pohditaan laiteliitynnän standardoinnin kehityssuuntia.

The objectives of this work were to find out what interfacing technologies and emerging standards can be adopted from the personal computer market to medical devices targeted for personal and home use, and to gain understanding of technical and regulatory limitations regarding their use in medical applications through implementing prototypes of these interfaces. The growing demand for home health care services, attributed to the increase in population of elderly people in the society, requires development of new remote and home health care systems and services which can utilize cost-effective PC technologies and devices already present at homes. The Thesis studies modern digital interface technologies, emerging standards and their use in medical devices. The interface technologies of interest are computer system peripheral interfaces and wireless personal area networking (PAN) technologies. The work aims at gaining understanding of technical and regulatory limitations and benefits regarding their use in medical applications, especially in personal health monitoring applications at home. Several steps are taken and prototypes built to assess the feasibility of these technologies and to obtain results usable in practical design cases. The Thesis also presents the current state of medical device regulation and standardization, of which the latter especially has been under rapid development over the recent years. Although the safety aspects of the developed implementations are addressed, the Thesis does not cover the full scope of risk analysis of networked medical devices or medical device software. The introductory part of the Thesis begins with the presentation of currently used digital interfaces and their design. Then, the medical device is defined, and safety, regulation, standardization, security, and privacy issues related to medical devices are presented, including current state of medical device interface standardization. Also, the use of PC and consumer electronics technology in medical devices and how medical device networking is changing the medical device design are discussed. The concept of personal health monitoring and its applications at home are presented, followed by a presentation of health monitoring needs and applications in various healthcare facilities. Finally, the direct contributions to the field of personal health monitoring system and device design contained in this work and derived conclusions are presented. A method for interfacing medical sensory devices of a commercial patient monitoring system to a standard PC was developed. This work shows how medical devices can be connected using a standard cable based (USB) interface, and presents different hardware implementation strategies and software related issues. Cable connected devices are more vulnerable to electrical hazards than wireless devices. This can be alleviated by electrical isolation of the cable interface. Different isolation strategies were studied and a method to isolate USB data signals was developed. A medical monitoring chair for ballistocardiogram (BCG) recording with a novel electromechanical film sensor based method was implemented both as a traditional analog amplifier design and as a wireless digital measurement system. The analog system was used in a clinical trial to gain experience of the medical device approval process. The digital system is shown to provide similar signal quality as the analog system with less costly equipment and with increased device mobility. The work also provides insight into the different data transfer needs of various human originated signals. Methods and technologies for wireless medical data-acquisition systems were studied and demonstrated. The application areas for wireless PAN devices in hospitals were surveyed and technologies assessed. The IEEE 802.15.4 wireless interface technology was selected for a wireless medical monitoring system (BCG chair) and further sensor network implementations. Networking of personal healthcare devices using the selected technology was studied by implementing a wireless sensor network. The interface technology was expanded to support networking by adding a Zigbee network communication protocol layer. Personal health monitoring devices were attached to the sensor network and fitted to a real-life home apartment. Current medical devices rely much on proprietary interfaces and even more on proprietary data presentation models making if often impossible to use devices from different manufactures together. The main claim of this work is that standardized interfaces should be used in medical devices to obtain reliable, safe, and more interoperable devices cost-effectively. A higher level standard to specify common nomenclature for physiological variables and to enable communication across different interface technologies is also needed, and attempts to develop one exist.

Price is an important criterion when new medical measurement instruments are purchased. Because of price competition manufacturers wish to use commercial off-the-self (COTS) products as much as possible. Regular office computers are well-suited for displaying and organizing patient measurement information. The most convenient way of connecting measurement devices to a computer would be via Universal Serial Bus (USB) or Ethernet plug, as they can be found from every modern computer. This thesis examines how USB could be used in a safe manner to connect a medial measurement instruments to regular office computer. Electrically operated medical instruments must have double insulation in order to protect the patient and medical personnel. In practice double insulation means that the device could be used safely even in case of 4 kV voltage applied to the mains power side. The easiest way to achieve the desired level of safety is to have electrical isolation with high breakdown voltage. Regular computer power supplies are normally not isolated. Changing the supply would not suffice if the computer is used also for other than medical instrumentation tasks. The isolation may be accidentally bypassed by for example connecting a non-isolated printer to the computer. Normally it is good to have isolation also between separate measurement units. In order to connect a medical instrument safely to a computer via USB there must be isolation either in the device or on the bus. This thesis presents an isolation implementation for the USB-signal within the device. With minor changes the isolation can be implemented also in USB-cable. The prototype isolation works in full-speed USB, which is 12 Mb/s version. Other speeds of the bus are also considered. All the changes needed to support speeds in the range of 1.5 - 480 Mb/s are described. Sairaalaympäristöön tarkoitettujen potilasmittalaitteiden hinta on usein merkittävä tekijä uusia laitteita hankittaessa ja voi ratkaista valinnan kahden tasapuolisen laitetoimittajan välillä. Hintapaineisiin vastatakseen laitevalmistajilla on halu käyttää toimistokäyttöön tarkoitettuja tietokoneita myös potilasmittauksista tulevan teidon jäsentämiseen ja näyttämiseen. Tiedonsiirto mittalaitteesta tietokoneeseen on helpointa järjestää jo valmiiksi tietokoneessa olevan liitynnän kautta. Nykyisin kaikissa tietokoneissa on Ethernet ja Universal Serial Bus (USB) -liitynnät. Tässä työssä tutkitaan USB-väylän soveltuvuutta potilasmittalaitteiden liittämiseen tavalliseen yleiskäyttöiseen tietokoneeseen. Sähkökäyttöisten potilasmittalaitteiden pitää olla kaksoiseristettyjä verkkovirrasta. Tämä tarkoittaa, että laitteen pitää toimia normaalisti ja turvallisesti, vaikka verkkovirran puolella esiintyisi 4 kV:n jännite. Helpoiten tämä saavutetaan riittävän jännitekestoisuuden omaavalla suojaerotuksella. Tavallinen tietokoneen virtalähde ei ole suojaerotettu. Myöskään pelkkä virtalähteen korvaaminen suojaerotuksella ei ole aina riittävä vaihtoehto, varsinkin jos tietokonetta halutaan käyttää myös muihin tehtäviin. Suojaerotus voidaan kiertää vahingossa esimerkiksi kytkemällä suojaerottamaton tulostin tietokoneeseen. Lisäksi usein halutaan erottaa eri mittaukset myös toisistaan. USB-väyläisten mittalaitteiden kytkeminen turvallisesti yleiskäyttöiseen tietokoneeseen edellyttää suojaerotusta mittalaitteessa tai USB-väylässä. Tässä työssä esitellään suojaerotuksen toteutus USB-väylän signaaleihin laitteen sisällä. Pienin muutoksin sama tekniikka soveltuu myös suoraan USB-johtimiin tehtävään suojaerotukseen. Suojaerotuksen prototyyppi toteutetaan USB-väylän full-speed versioon, eli 12 Mb/s nimellisnopeuden omaavaan versioon. Työssä käsitellään myös muiden nopeusluokkien suojaerotus ja esitetään tarvittavat muutokset siten, että yhdellä kytkennällä voidaan tukea nopeuksia 1,5 ja 480 Mb/s välillä. /Kir10