Enhancement of signal quality in esophageal recordings of diaphragm
emg.
Sinderby, Christer A., Jennifer C. Beck, Lars H.
Lindstr[diaeresis]om,and Alejandro E. Grassino,.
Meakins Christie Laboratories, McGill University, Montreal, Quebec,
Canada, and Notre Dame Hospital, University of Montreal, Montreal,
Quebec, Canada, and Spinal Injuries Unit, Sahlgrenska Hospital,
University of G[diaeresis]oteborg, G[diaeresis]oteborg, Sweden, and
Department of Medical Information Processing, Sahlgrenska Hospital,
G[diaeresis]oteborg, Sweden
APStracts 3:0576A, 1996.
The crural diaphragm electromyogram (EMG) is recorded from a sheet of
muscle whose fiber direction is mostly perpendicular to an esophageal
bipolar electrode. The region from which the action potentials are
elicited, the electrically active region of the diaphragm (EARdi),
and the center of this region, the EARdi center, may vary during
voluntary contractions, in terms of their position with respect to an
esophageal electrode. Depending on the bipolar electrode's position
with respect to the EARdi center, the EMGdi is filtered to different
degrees. The objectives of the present study were to reduce these
filtering effects on the diaphragm EMG by developing an analysis
algorithm referred to as the "double subtraction
technique". The results showed that changes in the position of
the EARdi center by +/-5 mm with respect to the electrode pairs
located 10 mm caudal and 10 mm cephalad, provided a systematic
variation in the EMG power spectrum center frequency values by +/
-10%. The double subtraction technique reduced the influence of
movement of the EARdi center relative to the electrode array on EMG
power spectrum center frequency and root mean square values,
increased the signal to noise ratio by 2 dB, and increased the number
of EMG samples that were accepted by the signal qulity indices by 50
percent.
Received 12 June 1996; accepted in final form 29 November 1996.
APS Manuscript Number A550-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996