Sinderby C A, Beck J C, Lindström L H, Grassino A E
Meakins Christie Laboratories, McGill University, Montreal, Quebec, Canada.
J Appl Physiol (1985). 1997 Apr;82(4):1370-7. doi: 10.1152/jappl.1997.82.4.1370.
The crural diaphragm electromyogram (EMGdi) is recorded from a sheet of muscle, the fiber direction of which is mostly perpendicular to an esophageal bipolar electrode. The region from which the action potentials are elicited, the electrically active region of the diaphragm (EAR(di)) and the center of this region (EAR(di ctr)) 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 EAR(di ctr), the EMGdi is filtered to different degrees. The objectives of the present study were to reduce these filtering effects on the EMGdi by developing an analysis algorithm referred to as the "double-subtraction technique." The results showed that changes in the position of the EAR(di ctr) 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 EAR(di ctr) 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 quality indexes by 50%.
小腿横膈膜肌电图（EMGdi）是从一片肌肉记录而来，这片肌肉的纤维方向大多与食管双极电极垂直。在自主收缩过程中，引发动作电位的区域、膈肌的电活动区域（EAR(di)）及其该区域的中心（EAR(di ctr)）相对于食管电极的位置可能会发生变化。根据双极电极相对于EAR(di ctr)的位置，EMGdi会受到不同程度的滤波处理。本研究的目的是通过开发一种称为“双减法技术”的分析算法来减少这些对EMGdi的滤波影响。结果表明，EAR(di ctr)相对于位于尾侧10毫米和头侧10毫米的电极对位置变化±5毫米时，EMG功率谱中心频率值会有±10%的系统性变化。双减法技术减少了EAR(di ctr)相对于电极阵列移动对EMG功率谱中心频率和均方根值的影响，使信噪比提高了2分贝，并使信号质量指标接受的EMG样本数量增加了50%。
