Oxygen maternal arterial partial pressure

In the placenta a volume of oxygen sufficient for fetal needs must diffuse across the membranes from maternal to fetal blood during the short time the two circulations are in close contact. This oxygen transfer is a function of several factors which include uterine and umbilical arterial 02 partial pressures, maternal and fetal placental blood flow rates, the 02 capacity and 02 affinity of maternal and fetal hemoglobin, the diffusing capacity of the placenta, the amount of C02 exchanged, and the vascular arrangement of maternal to fetal vessels. 

After it was determined that changing the linear velocity of the maternal or fetal blood stream did not affect the equilibration pressure, it was possible to determine the maternal to fetal volumetric flow rate ratio that would result in an equilibration pressure which matched experimentally determined values of umbilical vein and artery oxygen partial pressures (37). As the maternal to fetal volumetric flow rate ratio is increased, the partial pressure of oxygen at which equilibration... 

Figure 9 shows the effects of decreasing the oxygen capacity of maternal blood on the maternal axial oxygen partial pressure profile. In the normal case (N2 — 16 ml oxygen/100 ml blood) maternal arterial blood enters the exchange unit at an oxygen partial pressure of 90.5 mm... 

Figures 17 and 18 shows the effects produced on maternal and fetal blood when the arterial oxygen partial pressure of maternal blood is decreased.

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