Fetal cardiovascular simulations to assess the feasibility of intrauterine ECMO
E.A.M. Wachter (TU Delft - Mechanical Engineering)
J. Dankelman – Mentor (TU Delft - Medical Instruments & Bio-Inspired Technology)
Tom G. Goos – Mentor (TU Delft - Medical Instruments & Bio-Inspired Technology)
Manon Kok – Graduation committee member (TU Delft - Team Jan-Willem van Wingerden)
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Abstract
The placenta is very important during the start of life, providing the fetus with oxygen and nutrients from the maternal blood. Impaired growth of the placenta and additional placental ischaemia endangers the exchange of gasses, exchange of nutrients, and optimal growth of the fetus. This thesis investigates the feasibility of intrauterine ECMO to improve oxygen levels in fetal blood during placental ischaemia. Fetal blood would be retrieved from the umbilical artery, oxygenated in the ECMO system and fed back into the umbilical artery. The objective of this thesis is to design a cardiovascular model to simulate the cardiovascular response to an ECMO support system. A lumped parameter model is created to approximate the fetal cardiovascular system. By performing a parameter search, haemodynamic parameters were gathered for the fetal model. Data from 30 week fetuses was used as initial input, because of parameter accessibility. Parameters for the gestational age of 20 to 29 weeks were obtained by extrapolating the parameters from the fetus of 30 weeks with scaling factors. A sensitivity analysis was performed to analyse the flow and pressure distribution through the fetal cardiovascular system and the cardiovascular response to different parameters. Implementation of a cannula into one of the umbilical arteries increases the resistance of that artery. Simulating the cardiovascular response to the addition of the cannula showed promising results for the feasibility of intrauterine ECMO. The fetal heart is able to maintain blood flow through the cannula despite the fact that the resistance of the artery is increased. The placental resistance increases during placental ischaemia. Because of this higher resistance, blood flow through the placenta will decrease. However, even at a lower flow rate, oxygenation of blood flow via the umbilical artery is mostly sufficient. The reason is the high percentage of fetal cardiac output flowing through the placental circulation. The designed model is able to simulate the fetal cardiovascular system and provides a simulation tool to further develop an intrauterine ECMO support system.