THE FUTURE OF TELEMETRY IN CLINICAL MEDICINE

T. Penzel
Medizinische Poliklinik of Philipps-University, Baldingerstrasse, D-35033 Marburg

Telemetry in clinical medicine is well established in some specific applications. The well known field of application is ECG using RF telemetry within a hospital. There are some applications which use infrared telemetry for the transmission of different signals within short distances to free the patient from wires within a room, as it is used in sleep medicine and chronobiology research. This enhancement in patient comfort requires additional technical equipment and therefore is not very common. Another field of application is stimulation and the control of stimulators for nerves and muscles. A number of applications are found in this field, mainly in rehabilitation medicine. The introduction of new devices for neurostimulation reveals the importance of recording signals through conventional telemetry. A new stimulator recently introduced allows hypoglossal nerve stimulation in patients with obstructive sleep apnea to overcome the collapse of the upper airways during sleep. A pressure transducer is implanted in the manibrium of the patient to sense the negative intrathoracic pressure changes created during inspiratory efforts. This signal is analyzed and during the period of inspiration a pulse train of impulses is sent to an electrode connected to the hypoglossal nerve. This results in a protrusion of the tongue and thereby opens the upper airways leading to efficient breathing in this particular disorder. Telemetry is used to record the signals of respiration and to adapt the algorithm in the implanted pacemaker to the specific needs of the patient during the initial phase of treatment.

Beside these classical fields of telemetry the area of ambulatory monitoring and the new field of telemedicine applications are evolving rapidly taking advantage of improved technologies such as miniaturisation and reduction in power consumption. Nowadays many biological signals can be recorded using very small portable equipement and the load to carry for a patient does not exceed the weight of a cassette recorder. High capacity digital storage allows a high precision of recordings and preserves all signal characteristics if time and amplitude resolution were choosen apropriate.

The new field of telemedicine makes use of digital communication transmission. Theirby it is possible to equipe remote health care centers with simple recording equipment. The recorded biosignals such as ECG, EEG or even images can be transmitted using telephone networks to specialized centers for expert interpretation. This approach will be used increasingly, as no longer technology is the most expensive part but the medical experts expertise becomes more expensive in relation and is less available.

In conclusion, the field of clinical telemetry is moving from conventional applications, such as signal transmission, which is in common use in wildlife telemetry, towards ambulatory recording applications and systems which support telemedicine technologies. These new technologies support remote monitoring as well as remote control if desired.