Sieck G C, Mazar A, Belman M J
Respir Physiol. 1985 Aug;61(2):137-52. doi: 10.1016/0034-5687(85)90121-5.
Changes in electromyographic (EMG) activity of the diaphragm were examined in human subjects during different levels of voluntary hyperpnea. Diaphragmatic EMG was recorded using both surface and esophageal electrodes. The power spectra density (PSD) of the EMG signal was calculated and characterized by the high frequency to low frequency (H/L) ratio and by the centroid frequency (Fc). During high levels of voluntary hyperpnea, a significant decrease in both the H/L ratio and Fc occurred, which was similar in diaphragmatic EMG recorded by either surface or esophageal electrodes. This similarity in EMG spectral changes suggested that when diaphragmatic EMG was recorded using surface electrodes, there was only minimal contamination from the activity of other chest wall muscles. Changes in EMG Fc were detected during levels of hyperpnea which could be readily sustained. Thus, diaphragmatic EMG spectral changes were not characteristic of imminent ventilatory failure (i.e., an inability to sustain a target level of ventilation). In contrast, significant changes in EMG H/L ratio were observed only during hyperpneic loads which could not be sustained. This difference in sensitivity between the Fc and H/L ratio was due to the increased variability of H/L ratio and suggests that the H/L ratio may fail to detect small but significant shifts in EMG spectra. The relationship between the rate of decrease in EMG Fc and the level of hyperpnea was not statistically significant. We conclude that diaphragmatic EMG spectral changes do occur during hyperpneic loads, but we question the specificity of using diaphragmatic EMG spectral changes in predicting ventilatory failure.
在不同程度的自主过度通气期间，对人体受试者膈肌的肌电图（EMG）活动变化进行了检查。使用表面电极和食管电极记录膈肌EMG。计算EMG信号的功率谱密度（PSD），并通过高频与低频（H/L）比值和质心频率（Fc）进行表征。在高水平的自主过度通气期间，H/L比值和Fc均显著下降，这在使用表面电极或食管电极记录的膈肌EMG中是相似的。EMG频谱变化的这种相似性表明，当使用表面电极记录膈肌EMG时，其他胸壁肌肉活动的干扰最小。在能够轻松维持的过度通气水平期间检测到EMG Fc的变化。因此，膈肌EMG频谱变化并非即将发生通气衰竭（即无法维持目标通气水平）的特征。相比之下，仅在无法维持的过度通气负荷期间观察到EMG H/L比值的显著变化。Fc和H/L比值之间这种敏感性差异是由于H/L比值变异性增加所致，这表明H/L比值可能无法检测到EMG频谱中微小但显著的变化。EMG Fc下降速率与过度通气水平之间的关系无统计学意义。我们得出结论，在过度通气负荷期间确实会发生膈肌EMG频谱变化，但我们质疑使用膈肌EMG频谱变化预测通气衰竭的特异性。
