Fujii Y, Oshima T, Toyooka H, Udagawa T, Ebata T, Amaha K
Department of Anesthesiology and Critical Care Medicine, Tokyo Medical and Dental University, School of Medicine.
Masui. 1991 Aug;40(8):1245-50.
Effects of highly decreased cardiac output on the development and recovery of diaphragmatic fatigue were studied in dogs. The fatigue was induced by supramaximal electrical stimulation (20 Hz) of phrenic nerves for 30 minutes. Cardiac output was reduced during this period to 30% of control value by mechanically obstructing inferior vena cava with a balloon in animals with lowered cardiac output group (lowered Qt group). Cardiac output was maintained at normal value throughout the experiment in animals of the other group (control group). The animals were observed for recovery for 60 minutes after induction of the fatigue. The standardized transdiaphragmatic pressure (Pdi/Pdi 100) and integrated electromyographic activity (Edi/Edi 100) elicited by electrical test stimuli (20, 100 Hz) were significantly lower in lowered Qt group (P less than 0.01) during entire fatigue and recovery period. The decrease of Pdi/Pdi 100 and Edi/Edi 100 at high frequency test stimuli (100 Hz) was observed only in lowered Qt group. These results suggest that when cardiac output is severely decreased the diaphragm is more susceptible to fatigue, and that this may be caused by a failure of neuromuscular junction as well as by an impaired excitation-contraction coupling.
在犬类动物中研究了心输出量大幅降低对膈肌疲劳发生及恢复的影响。通过对膈神经进行超最大强度电刺激（20赫兹）30分钟来诱发疲劳。在心输出量降低组（降低Qt组）动物中，在此期间通过用球囊机械阻塞下腔静脉，使心输出量降至对照值的30%。另一组动物（对照组）在整个实验过程中心输出量维持在正常水平。在诱发疲劳后观察动物60分钟的恢复情况。在整个疲劳和恢复期间，降低Qt组中由电测试刺激（20、100赫兹）诱发的标准化跨膈压（Pdi/Pdi 100）和肌电图积分活动（Edi/Edi 100）显著更低（P小于0.01）。仅在降低Qt组中观察到高频测试刺激（100赫兹）时Pdi/Pdi 100和Edi/Edi 100的降低。这些结果表明，当心输出量严重降低时，膈肌更容易疲劳，这可能是由神经肌肉接头功能障碍以及兴奋 - 收缩偶联受损所致。
