Doud J R, Dornseif S E, Walsh J M
Division of Pulmonary and Critical Care Medicine, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois.
J Appl Physiol (1985). 1994 Apr;76(4):1830-5. doi: 10.1152/jappl.1994.76.4.1830.
The electromyogram (EMG) power spectrum from spontaneous diaphragm contractions has been used to identify the development of fatigue. However, power spectral analysis of the spontaneous diaphragmatic EMG signal is limited and subject to error. In contrast, power spectral analysis of the compound diaphragm action potential (CDAP) may be superior. The aim of the present study was to determine whether the EMG power spectra of evoked CDAPs correlate with those of spontaneous diaphragm contractions. Four anesthetized mechanically ventilated dogs with spontaneous isometric diaphragm contractions were studied using a mechanically isolated in situ diaphragm preparation. CDAPs were elicited via phrenic nerve stimulation, and intramuscular wire electrodes recorded EMG. Diaphragm temperature was changed from 40 to 30 degrees C to elicit changes in the EMG power spectra. The EMG signal from 10 spontaneous contractions and 10 CDAPs were acquired at 1 degrees C intervals. Fast Fourier transform was applied to both spontaneous and CDAP data yielding the power spectra, which were represented by their center frequencies (fc). The CDAP fc correlated well with the EMG fc obtained from spontaneous contractions (r = 0.99). We conclude that evoked CDAPs may provide an accurate alternative to spontaneous contractions for EMG power spectral analysis of the diaphragm.
来自自发性膈肌收缩的肌电图（EMG）功率谱已被用于识别疲劳的发展。然而，自发性膈肌EMG信号的功率谱分析存在局限性且容易出错。相比之下，复合膈肌动作电位（CDAP）的功率谱分析可能更具优势。本研究的目的是确定诱发CDAP的EMG功率谱是否与自发性膈肌收缩的功率谱相关。使用机械隔离的原位膈肌制备方法，对四只麻醉状态下机械通气且有自发性等长膈肌收缩的犬进行了研究。通过膈神经刺激诱发CDAP，并使用肌内线状电极记录EMG。将膈肌温度从40℃改变至30℃以引发EMG功率谱的变化。以1℃的间隔采集10次自发性收缩和10次CDAP的EMG信号。对自发性和CDAP数据均应用快速傅里叶变换以生成功率谱，功率谱由其中心频率（fc）表示。CDAP的fc与从自发性收缩获得的EMG的fc具有良好的相关性（r = 0.99）。我们得出结论，对于膈肌的EMG功率谱分析，诱发的CDAP可能是自发性收缩的一种准确替代方法。
