INFLUENCE OF THE BIPOLAR ELECTRODE TRANSFER-FUNCTION ON THE ELECTROMYOGRAM POWER SPECTRUM

This study demonstrates the impact of the bipolar electrode transfer f unction on the canine diaphragm electromyogram (EMG) power spectrum, a s evaluated with a new electrode design and implantation technique, Th e results show that: (a) changes in interelectrode distance transforme d single-peaked power spectrums into double-peaked spectrums; (b) the mean action potential conduction velocity (<(APCV)over bar>), and powe r spectrum center frequency (CF) and median frequency (MF), are relate d for interelectrode distances of 5 and 10 mm, but not for 15 and 20 m m; and (c) CF, MF, - 3-dB, and - 6-dB bandwidth values depend on inter electrode distance. We conclude that bipolar electrodes, with a nonfix ed interelectrode distance, cannot be used for physiological interpret ations of the EMG power spectrum. Nonetheless, power spectrums obtaine d with fixed and appropriate interelectrode distances can be trusted, if the electrodes are positioned in the direction of the muscle fibers and in regions with low densities of motor endplates. (C) 1996 John W iley & Sons, Inc.