Brett Harnett
Center for Surgical Innovation, University of Cincinnati

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1. Introduction

The practice of telemedicine can be divided into two distinct categories: realtime and store-and-forward. Realtime telemedicine involves synchronous interaction between the parties concerned. For example, a health-care professional and a patient may interact by videoconferencing. While realtime telemedicine is often effective in terms of consultation and patient satisfaction,[1][2] it presents challenges. Foremost is the scheduling of the parties concerned, because there are usually two health-care providers involved in the consultation (the local provider and the remote physician), and they both need to be available at the same time.

In contrast, store-and-forward (S&F) telemedicine is an asynchronous interaction, so that a clinical query, for example, can be transmitted by the referrer and then answered by a specialist at a convenient time. Email is a common example of this type of telemedicine. Although diagnostic accuracy may be lower with S&F telemedicine, it is advantageous from the point of view of cost, complexity and convenience.[3]

The field of telemedicine encompasses more than clinical interactions, of course. Having the technology to connect remote sites also allows distance learning. This may involve training or information sharing for health-care professionals that does not directly involve patients but still enhances care.

2. Essential Components of a Telemedicine System

Successful telemedicine requires appropriate equipment and some kind of telecommunications medium. However, successful telemedicine requires more than just technology. The three essential components are:

1. the personnel,
2. the technology,
3. a liberal measure of perseverance.

2.1 Personnel

For any telemedicine system to work in practice - in a real clinical situation - suitable, committed personnel are essential. People with the necessary skills to undertake the clinical components are required at both ends of any telemedicine link. This means that there must be trained staff at the referring end of the link who are able to handle the patient contact required. They must be comfortable with this mode of care delivery and they will probably need prior training, since telemedicine will represent a clinical situation that they are not normally exposed to. Unless this is planned in advance, the technology may be underused (or even ignored entirely) by staff who may be uncomfortable with the new processes.

At the specialist, or consulting, end of a telemedicine link, different characteristics are required of the personnel. The two most important factors are the reliability of the equipment and the availability of the appropriate personnel. Use of a telemedicine system will decrease if the patient information is available but the link is unusable, either for technical reasons or because the appropriate staff are not available at the diagnostic end. It is essential to ensure that there are sufficiently trained personnel and the schedules are carefully planned to enable links to be used with minimum delays, even in emergencies. Training is a very important factor in successful telemedicine.[4]

2.2 Technology

The technology is in many ways the most straightforward part of a telemedicine system and, once a working link has been established, it can largely be ignored. Much of the equipment required may already be available for other functions, and can be shared if planned properly. Reliability is a requirement for all medical equipment and telemedicine equipment is no exception. For telemedicine, all the equipment needs to function properly, since any malfunction will break the chain required for a successful link. Although modern computers and operating systems are fairly reliable, the integration of components still requires close attention to ensure reliability and ease of use. Unreliable technology is likely to cause the system to be under-used or even ignored.

2.3 Perseverance

Finally, it is important to mention one crucial component, without which a telemedicine system will not function. Experience shows that at least one dedicated and committed individual is needed with the perseverance to overcome the inertia inherent in all established clinical routines, and the commitment to champion the new system until it can demonstrate its usefulness. This mentor or champion of the system will help to drive the implementation and to deal with problems as they arise.[5]

3. Clinical Requirements

The technology required for a telemedicine link can be divided into three categories:

1. equipment to capture the clinical information at each site,
2. the telecommunications link needed to transmit this information between the sites,
3. equipment to display the information at each site.

Before the technology can be selected, it is necessary to consider the nature of the information to be transmitted between the sites, because this will determine the choice of equipment and the telecommunications network. Factors to be considered include:

1. the types of information to be transmitted,
2. the quantity of information to be transferred,
3. security and privacy (e.g. in Europe and the USA there has been recent legislation about data security).

3.1 Types of Information to be Transmitted

Different clinical situations generate very different types of clinical information (Table 1). Hence, there are many possible sources of data that can be used in telemedicine applications. In some cases this can be relatively simple information, such as concentrations of a metabolite (e.g. a high blood glucose concentration may suggest diabetes), whereas in others more qualitative and subtle information is needed, as in psychiatric assessments, where observations of posture, speech and mental state are required. Not all information will be needed at every site. For example, a telepsychiatry application will probably require ordinary commercial videoconferencing equipment instead of very high-quality audio or video signals and a telemonitoring service will require only data and text transfer, without audio and video.

Information Source	Type	Typical File Size
Electronic Stethoscope	Audio	100 kByte
ECG Recording	Data	100 kByte
Chest X-Ray	Still Image	1 MByte
Fetal Ultrasound Recording (30 s)	Moving Image (video)	10 MByte

Table 1: Examples of Clinical Information

The clinical need for any telemedicine project must be carefully assessed before making decisions about what equipment will be required. In the past, projects have been established on the assumption that it will be necessary to transmit all possible types of information. This can lead to disproportionately high set-up and maintenance costs that may not be justified by the actual telemedicine use. In general, it is preferable to limit the initial system to a defined clinical goal and so minimize the costs.

3.2 Quantity of Information Transferred

The units in which the quantity of digital information is measured are the bit and the Byte (Box 1). One method by which the total volume of information can be reduced is to compress it first, and then decompress it on reception. This is not always an acceptable technique for medicolegal reasons (i.e. only the original raw signal may be considered acceptable).

A careful assessment of the above needs will determine the quantity of information that must be transmitted between the project sites, and the time frame over which it must be sent to achieve the desired clinical goals. In S&F applications, the transmission time may not be important; in realtime applications, the transmission time is usually critical.

Once this fundamental aspect has been established, it will then be possible to assess whether there is a technically feasible means of achieving it. In practice, some solution is almost always possible, but the costs may not be justified by the clinical benefit.

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