CHEST-WALL MUSCLE CROSS-TALK IN CANINE COSTAL DIAPHRAGM ELECTROMYOGRAM

The present paper describes the influence of cross tails from the abdo minal and intercostal muscles on the canine diaphragm electromyogram ( EMG). The diaphragm EMG was recorded with bipolar surface electrodes p laced on the costal portion of the diaphragm (abdominal side), aligned in the fiber direction, and positioned in a region with a relatively low density of motor end plates. The results indicated that cross talk may occur in the diaphragm EMG, especially during conditions of loade d breathing and light general anesthesia. The cross-tails signals show ed characteristics that were entirely different from tho diaphragm EMG . Although the diaphragm EMG was typical for signals recorded with ele ctrodes aligned in the fiber direction, the cross-talk signals were ch aracteristic of those obtained with electrode pairs not aligned in the direction of the muscle fibers. Alterations in electrode positioning, interelectrode distance, and/or electrode surface area cannot guarant ee the elimination of crosstalk signals, whereas spinal anesthesia at a high thoracic level will paralyze the sources of the cross talk and hence eliminate the cross-talk signals. By taking advantage of the dif ferences in EMG signal characteristics for the diaphragm EMG and cross -talk signals, an index that has the capability to detect cross talk w as developed.