Educational simulation of the oxygen delivery to the fetus

Abstract

Introduction Maternal hypotension or cardiac arrest, maternal hypoxia associated to ventilatory complications, and fetal asphyxia caused by compression of the umbilical cord are examples of critical situations in obstetrics and in anaesthesia of the pregnant woman. These incidents are rare and associated with a high risk to the woman and fetus. Therefore, simulation is a valuable tool in teaching the diagnostic and therapeutic skills in this context. The target audience of such simulations consists of residents in obstetrics and anaesthesia, midwives and nurse anaesthetists in training. We described a component of a simulator for fetal distress, namely a mathematical model for the educational simulation of the oxygen delivery to the fetus [1]. This abstract outlines this model and the main simulation results. Methods The underlying physiology is represented using a multiple modeling approach ( Fig. 1). The haemodynamic model simulates the uterine, placental and umbilical blood flow rates as a function of maternal and fetal blood pressures. The model parameter: resistance to umbilical cord blood flow rate permits simulation of occlusion. The flow rates of the haemodynamic model are inputs to the oxygen uptake and distribution model. This model simulates the O2 supply to the placenta, the exchange of O2 across the placental barrier, the O2 transport in the umbilical cord, and the fetal O2 consumption. The differences in O2 dissociation between maternal and fetal blood are taken into account. Model parameters for the human placenta and fetus were found in the literature [2]. To validate the model response to simulated critical situations we used fetal lamb data, as no data on humans were available. 1 Model block diagram. Results Figure 2 shows the model output: O2 partial pressure in the fetal arterial blood, following simulated maternal hypotension [1] and partial occlusion of the umbilical cord [2]. The reduction in partial pressure for these two situations compares favourably with data from the literature [3,4]. 2 Simulation results.