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目前所知的胎儿循环状态主要基于动物试验及未成活胎儿。其结论可能与人类成活胎儿状况有异。多普勒超声可提供一可靠的非侵犯性估计胎儿血流状况的手段,能充分观察正常和异常的血流循环状态。一、胎儿循环特点及脐带血流动力学胎儿循环系统对维持氧供、营养交换、支持胚胎生长起重要作用。其主要特点为: (1)存在胎儿胎盘循环;(2)存在血管通路,此通路在产后消失(如脐血管、静脉导管、卵圆孔)。由于胎儿胎盘循环的存在构成降主动脉——下腔静脉血流动力学途径中的一个最大阻抗。脐带的平均动脉压随孕周的增加而增加,因而保证血流量也逐渐增加。随着胎儿循环系统的逐渐成熟,由中枢
The current state of fetal circulation is mainly based on animal experiments and unborn fetuses. The conclusion may be different with the human fetus survival status. Doppler ultrasound provides a reliable, noninvasive means of estimating fetal blood flow, allowing adequate observation of normal and abnormal blood flow circulation. First, the characteristics of fetal circulation and cord blood flow dynamics The fetal circulatory system to maintain oxygen supply, nutrition exchange, support embryo growth plays an important role. Its main features are: (1) the existence of fetal placental circulation; (2) the existence of vascular access, disappearance of this pathway after delivery (such as umbilical blood vessels, intravenous catheter, foramen ovale). The presence of the fetal placenta constitutes a maximum impedance in the descending aorta-inferior vena cava hemodynamics pathways. The mean arterial pressure of the umbilical cord increases with gestational age, thus ensuring that the blood flow increases gradually as well. As the fetal circulatory system gradually matures, by the center