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CMAP variability as a function of electrode site and size
Author(s) -
Van Dijk J. Gert,
van der Kamp W.,
TjonATsien Aimee
Publication year - 1995
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880180110
Subject(s) - electrode , compound muscle action potential , coefficient of variation , amplitude , percentile , forearm , electrophysiology , biomedical engineering , materials science , anatomy , chemistry , medicine , mathematics , physics , statistics , optics
The site of the recording electrode influences the amplitude of the compound muscle action potential (CMAP) and its variation over a length of nerve. The effects of large electrodes on this source of intra‐individual variability were assessed. Right median nerves of 20 healthy subjects were studied, and recordings made at three sites (at 1‐cm intervals) using five electrode sizes (0.01, 1, 2, 4, and 10 cm 2 ). Site‐induced variability was defined as the standard deviation (SD i ) and coefficient of variation (CV i ) of the measurements of the three sites. Site induced variability of all parameters (latency, duration, amplitude, area, MNCV, and the percentile changes of duration, amplitude, and area over the forearm) decreased significantly with electrode size. Decreases were most pronounced for amplitude and area: CV i fell from 29% and 30% (0.01‐cm 2 electrode) to 10% and 8% (10 cm 2 ). It is argued that large electrodes record activity of more motor units than small electrodes, and that their measurement fields overlap to a greater extent. The use of large electrodes is recommended in order to reduce site‐induced CMAP variability.© 1995 John Wiley &Sons, Inc.