Stone D N, Dujardin J P
Am J Physiol. 1984 Jan;246(1 Pt 2):H1-7. doi: 10.1152/ajpheart.1984.246.1.H1.
Experiments were performed on anesthetized dogs to quantitate the effects of changes in aortic smooth muscle tone on the passive pressure dependence of the aortic characteristic impedance (Zc). Zc was calculated from the diastolic pressure-diameter relationship in a wide pressure range induced by forced slow oscillations in pressure. Changes in aortic smooth muscle activity were induced by hemorrhage (-15% of the estimated blood volume), by volume expansion (+15 and +30%), and by alpha-adrenergic blockade. Curves relating Zc to pressure showed a minimum in the physiological pressure range and were well described by parabolas under all conditions. Under control conditions, the minimum Zc pressure was located close to the mean arterial pressure. Both levels of volume expansion as well as alpha-blockade reduced Zc at all pressure levels. Hemorrhage increased Zc at each pressure level and caused the minimum in the Zc vs. pressure curves to shift to higher values. The observed changes in Zc may play an important role in the hemodynamic adjustments to hemorrhage and to volume expansion.
在麻醉犬身上进行实验，以定量主动脉平滑肌张力变化对主动脉特性阻抗（Zc）被动压力依赖性的影响。Zc是根据在压力强迫缓慢振荡诱导的宽压力范围内的舒张压-直径关系计算得出的。通过出血（估计血容量的-15%）、容量扩张（+15%和+30%）以及α-肾上腺素能阻断来诱导主动脉平滑肌活动的变化。将Zc与压力相关的曲线在生理压力范围内呈现最小值，并且在所有条件下均能用抛物线很好地描述。在对照条件下，最小Zc压力接近平均动脉压。两种水平的容量扩张以及α-阻断在所有压力水平下均降低了Zc。出血在每个压力水平均增加了Zc，并导致Zc与压力曲线的最小值向更高值移动。观察到的Zc变化可能在对出血和容量扩张的血流动力学调节中起重要作用。
