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Background: Many practice guidelines recommend using
a peripheral nerve stimulator during anesthesia with
muscle relaxants to improve patient safety; however it is
not widely available in our country. Thus, a locally
manufactured peripheral nerve stimulator was designed.
This study was aimed to evaluate the electrical characteristics
and accuracy of these peripheral nerve stimulators.
Materials and methods: Peripheral nerve stimulators
(TOF-watch and Thai locally-manufactured) were set to
deliver a train of four stimulation at 50 mA currents into a
resistance loads ranging from 500 to 7000 ohm which
represented the range of patient skin resistance, in same
standard temperature and relative humidity. The current
output, stimulus duration, waveform morphology, and
maximum voltage output were studied using a factorycalibrated
Results: The stimulation was performed 66 times for each
peripheral nerve stimulator. One sample t-test demonstrate
the current output was higher than set current (50mA) in
both models (P < 0.001, 2.207 [2.050-2.365] vs 3.993
[3.643-4.343] for TOF-watch and Thai peripheral nerve
stimulator respectively). These small differences of the
stimulus current output should not affect clinical
measurement. The morphology of the stimulus performed
by both models was characterized by a regular monophasic
rectangular pulse at all resistance loads. However, both
mean rise time (17.18 vs 6.86 microseconds) and decay
time (13.12 vs 1.44 microseconds) were lower in Thai
peripheral nerve stimulator (P < 0.001).
Conclusions: According to the electrical characteristic
measurement from this study, the Thai peripheral nerve
stimulator was comparable to TOF-watch and further use
in patients should be studied.
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