Heart Research Group, Murdoch Children's Research Institute, Melbourne, Australia.
J Appl Physiol (1985). 2011 May;110(5):1362-73. doi: 10.1152/japplphysiol.00038.2011. Epub 2011 Mar 10.
Although the distribution of average fetal pulmonary trunk (PT) blood flow favors the ductus arteriosus (DA) over the lungs, the phasic aspects of this distribution during systole and diastole are not well understood. Accordingly, flow profile and wave intensity (WI) analyses were performed at baseline and during brief flow increases accompanying an extrasystole (ES) in 10 anesthetized late-gestation fetal sheep instrumented with PT, DA, and left pulmonary artery (PA) micromanometer catheters and transit-time flow probes. At baseline, 83% of mean PT flow crossed the DA and 17% entered the lungs. However, early systolic flow associated with a forward-running compression wave (FCW(is)) was higher in the PA and predominant DA flow only emerged in midsystole when a large PA backward-running compression wave (BCW(ms)), which reduced PA flow, was transmitted into the DA as a forward-running compression wave (FCW(ms)) that increased flow. Subsequent protodiastolic forward DA flow occurring during pulmonary valve closure was associated with substantial retrograde PA flow, but insignificant PT flow. Conversely, forward DA flow in the remainder of diastole occurred with forward PT but near-zero PA flow. These flow and WI patterns, in conjunction with the results of mathematical modeling, suggest that 1) fetal PT flow preferentially passes into the PA during early systole due to a lower PA-than-DA characteristic impedance, while DA flow predominates in mid- and late systole due to flow effects arising from the PA BCW(ms), and 2) forward DA flow is mainly sustained by reversal of PA flow in protodiastole but discharge of a more central reservoir in diastole.
尽管平均胎儿肺动脉（PT）血流的分布有利于动脉导管（DA）而不是肺部，但在收缩期和舒张期，这种分布的时相方面还没有得到很好的理解。因此，在 10 只麻醉的晚期妊娠绵羊中，在基础状态下以及在伴随期前收缩（ES）的短暂血流增加期间，对 PT、DA 和左肺动脉（PA）测压导管和传输时间流量探头进行了流量剖面和波强（WI）分析。在基础状态下，83%的平均 PT 血流穿过 DA，17%进入肺部。然而，与正向运行的压缩波（FCW(is)）相关的早期收缩期血流在 PA 中较高，并且只有在大的 PA 反向运行的压缩波（BCW(ms)）传入 DA 中作为增加流量的正向运行的压缩波（FCW(ms)）时，主要的 DA 血流才会出现在收缩中期。随后，在肺动脉瓣关闭期间发生的舒张早期正向 DA 血流与大量逆行 PA 血流相关，但与 PT 血流无关。相反，在其余的舒张期内，向前的 DA 血流发生在向前的 PT 但几乎为零的 PA 血流。这些流量和 WI 模式，结合数学模型的结果，表明 1）由于 PA 的特征阻抗低于 DA，胎儿 PT 血流在早期收缩期优先进入 PA，而在中晚期收缩期由于来自 PA BCW(ms)的流量效应，DA 血流占主导地位；2）在舒张早期，主要通过逆行 PA 血流的逆转来维持正向 DA 血流，但在舒张期，从更中心的储器中排出。
