Digitimer Ltd - DS8R Operator’s Manual
Version 2.0
8
Digitimer Ltd.
Copyright ©2019
Do NOT stimulate over the carotid sinus nerves, neck and mouth. Stimulation should not be applied
over carotid sinus nerves, particularly in patients with a known sensitivity to the carotid sinus reflex.
Severe spasm of the laryngeal and pharyngeal muscles may occur and the contractions may be
strong enough to close the airway or cause difficulty in breathing.
Subject Exclusion Criteria
Subjects fitted with an implanted electronic device such as a cardiac pacemaker should NOT be
stimulated unless specialist medical opinion has been obtained.
Needle Electrodes
Please note that where “stimulation” or “transcutaneous stimulation” is referred to in this
document, it means “electrical stimulation through the skin” and NOT the use of skin penetrating
needle electrodes.
The use of needle electrodes is NOT recommended, due to the possibility of high current densities at
stimulation sites.
Electrode Isolation
The following generally applies to the use of nerve and muscle stimulators, and especially those
designed for transcutaneous use. See, for example, the section on Safety of Apparatus in Guld et al,
1970
1
. It is essential for safety that the connections from the stimulator to the subject are isolated
from earth/ground, and this means that an earth/ground connection must not be made to either
terminal on the stimulator or to either stimulating electrode. Similarly, it is undesirable to place an
earth/ground electrode on the subject close to one of the stimulating electrodes. It is also important
that an unintentional path to earth/ground should not be introduced by attempts to monitor the
stimulating current, or in any other way. As an instance of such dangers, it is likely that when using
the DS8R stimulator with recording apparatus, it will be necessary to have an earth/ground
electrode on the subject somewhere in the vicinity of the recording electrodes. If a second
earth/ground connection was to be made to one of the stimulating electrodes, current could flow
between the other stimulating electrode and the recording earth/ground electrode. Since the
recording site would be some distance from the stimulating site, structures other than those
between the stimulating electrodes, e.g. the heart, might be reached by the unintended spread of
current via the recording earth/ground electrode. It is important, therefore, that the output
terminals of the DS8R stimulator are only connected to the stimulating electrodes and to nothing
else. Attempts to measure the stimulus current, by inserting a resistor into one stimulating lead and
using an oscilloscope to measure the voltage drop across the resistor, are likely to violate the rule of
not connecting a path to earth/ground to either side of the stimulator output. The safe way to
monitor the stimulating current (should this be necessary) is by means of a suitable (Medical grade)
current transformer, preferably of the clip on type, which can be clipped over one of the stimulator
output leads.
1
Guld, C., Rosenfalk, A., and Willison, R. G. (1970), Technical factors in recording electrical activity
of muscle and nerve in man. Electroenceph. Clin. Neurophysiol., 28:399-413.
Output Enable
An operational protocol should be established whereby the “Output Enable” switch of the DS8R is
only switched to “ON / enabled” when delivery of a stimulus is specifically required.
Modification
WARNING - Do NOT modify this equipment without authorization of the manufacturer.
