Gilbert R D
Am J Physiol. 1980 Jan;238(1):H80-6. doi: 10.1152/ajpheart.1980.238.1.H80.
Changes in cardiac output (Qco), heart rate, right atrial pressure, (Pra), and mean systemic pressure (Pms) in response to blood volume changes were measured in chronically prepared fetal sheep. With a 10% decrease in blood volume, fetal cardiac output, measured with the microsphere technique, decreased significantly from 592 +/- 28 to 471 +/- 32 ml . min-1 . kg-1. Heart rate changed little from control animals (163 +/- 5) to those with decreased volume (161 +/- 10 beats/min). Right atrial pressure decreased significantly from 5.4 +/- 0.4 to 4.2 +/- 0.6 mmHg. Mean systemic pressure decreased from 13.8 +/- 0.3 to 10.5 +/- 0.6 mmHg. With a 10% increase in fetal blood volume, cardiac output rose insignificantly to 632 +/- 38 ml . min-1 . kg-1. However, right atrial pressure increased significantly to 8.9 +/- 0.6 mmHg and mean systemic pressure increased significantly to 16.5 +/- 0.8 mmHg with the increased volume. Heart rate again changed little (153 +/- 9 beats/min). The fact that cardiac output rose only a small amount, whereas right atrial pressure rose sharply with an increased blood volume, suggests that the fetal heart is operating near the upper limit of its Starling function curve. As a result, there is very limited cardiac reserve for increases in fetal cardiac output.
在长期制备的胎羊中，测量了心输出量（Qco）、心率、右心房压力（Pra）和平均体循环压力（Pms）对血容量变化的反应。血容量减少10%时，用微球技术测量的胎儿心输出量从592±28显著降至471±32 ml·min⁻¹·kg⁻¹。心率从对照动物（163±5）到血容量减少的动物（161±10次/分钟）变化不大。右心房压力从5.4±0.4显著降至4.2±0.6 mmHg。平均体循环压力从13.8±0.3降至10.5±0.6 mmHg。胎儿血容量增加10%时，心输出量无显著升高至632±38 ml·min⁻¹·kg⁻¹。然而，随着血容量增加，右心房压力显著升高至8.9±0.6 mmHg，平均体循环压力显著升高至16.5±0.8 mmHg。心率再次变化不大（153±9次/分钟）。心输出量仅少量增加，而随着血容量增加右心房压力急剧升高，这一事实表明胎儿心脏在其斯塔林功能曲线的上限附近运作。因此，胎儿心输出量增加时心脏储备非常有限。
