Dujardin J P, Stone D N, Forcino C D, Paul L T, Pieper H P
Am J Physiol. 1982 Feb;242(2):H197-202. doi: 10.1152/ajpheart.1982.242.2.H197.
Experiments were performed on eight anesthetized dogs to study the response of the characteristic impedance (Zc) of the main pulmonary artery to changes in circulating blood volume. Pressure and flow were measured in the proximal main pulmonary artery under control conditions, after hemorrhage (-15% of the estimated blood volume), again under control conditions, and finally after volume expansion (+30% of the estimated blood volume). Two different methods were used to determine Zc from these recordings. With the frequency-domain method values for Zc were obtained by averaging the input impedance moduli between 2 and 15 Hz. With the time-domain method Zc was derived as the slope of the early ejection pressure-flow relationship. The values for Zc obtained with the two methods were not statistically different. In the time-domain method the average increase in Zc with hemorrhage was 30.7 +/- 7.4 (SE) %, and the average decrease with volume expansion was -21.1 +/- 5.0 (SE) %. Because the time-domain method allowed the values of Zc during control conditions and after hemorrhage to be obtained in the same pressure range, it was concluded that the observed changes were caused by a change in the activity of the smooth muscle in the pulmonary arterial wall. Similarly, it was concluded that the decrease in Zc after volume expansion was active in nature.
对八只麻醉犬进行实验，以研究主肺动脉特征阻抗（Zc）对循环血容量变化的反应。在对照条件下、出血后（估计血容量的 -15%）、再次对照条件下以及最后容量扩张后（估计血容量的 +30%），测量主肺动脉近端的压力和流量。使用两种不同方法从这些记录中确定Zc。采用频域法时，通过平均2至15Hz之间的输入阻抗模量获得Zc值。采用时域法时，将Zc推导为早期射血压力 - 流量关系的斜率。两种方法获得的Zc值无统计学差异。在时域法中，出血时Zc的平均增加为30.7±7.4（标准误）%，容量扩张时平均减少为 -21.1±5.0（标准误）%。由于时域法能够在相同压力范围内获得对照条件下和出血后的Zc值，因此得出结论，观察到的变化是由肺动脉壁平滑肌活动的改变引起的。同样，得出结论，容量扩张后Zc的降低本质上是主动的。
