IMPLANT TELEMETRY AND STIMULATION 
Wen H. Ko* 
In some experimental procedures it is desirable to 
minimize disturbance of the animal under study by 
eliminating wires and other restraints, particularly for 
long term continuous experiments. In these cases, im- 
plant telemetry and stimulation can be considered. The 
added complexity, cost and possible technological diffi- 
culties should be justified by reduced interference with 
the subject. With advances in solid state electronic de- 
vice technology, technical difficulties are being solved 
and implant electronic devices are expected to become 
important experimental instruments in the future. 
INTRODUCTION 
With the development of microelectronics and 
solid state device technology, electronic instru- 
ments can be made small and light enough to be 
implanted in the body of a living subject to per- 
form measurements, stimulation, and control 
functions. The implant instrument is a valuable 
experimental technique for animal study and 
medical research and is becoming an acceptable 
device for diagnostic and therapeutic purposes. 
Advantages of implant instruments are: (1) 
minimum restriction or interference with the 
subject, and (2) long term operation vi^ithout 
cross skin connection. The disadvantages in- 
clude: (1) difficulty in designing small and light 
weight instruments, which raises the cost, (2) 
surgery and application skill, (3) the need to de- 
velop packaging material and long term power 
supplies, and (4) the lack of data on reliability 
and side effects of instruments and techniques 
being developed. 
Implant instruments can be grouped into (1) 
telemetry for in vivo measurements; (2) stim- 
ulation, for generation of desired body response 
in vivo;- (3) closed loop control systems; and 
(4) remote control manipulators. Telemetry 
and stimulation units are well developed for 
animal studies at the present. The implant con- 
♦ Engineering Design Center, Case Western Reserve University, 
Cleveland, Ohio 44106. 
trol system and manipulators may be useful 
techniques for the future medical research. The 
use of implant instrumentation should be justi- 
fied by weighing the benefits and cost to the 
experiment on an individual care basis. The 
major applications are as follows. 
Animal study for physiology, pharmacology 
and disease 
Implant instruments can provide nearly nor- 
mal environment while the subject assumes 
regular activity. Continuous telemetering of 
body information can be obtained over a period 
of weeks, months, or even years. Desired body 
response can be controlled by electrical stimula- 
tion over a long period at a remote location. The 
implant heart pacemaker and blood pressure 
regulating device to control blood pressure are 
commercially available. Many other stimulators 
are being developed, including stimulators for 
bladder, brain, muscle, implantable visual aid 
for the blind and anesthesia machines, etc. 
These can be used for animal study as well as 
clinical applications. 
Long term monitoring 
Physiological parameters deep in the body of 
experimental subjects and patients may need 
to be monitored over a long period. For example, 
in the study of transplanted or artificial heart 
components, such as artery and valve sections, 
implant instruments may be used to monitor 
the flow, blood pressure, and other performance 
of these components. 
Closed Loop Control System 
An implant closed loop control system has 
many applications for biological investigation, 
such as the study of body regulations or sub- 
stitution of a damaged control loop in the body 
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