Fetal Oxygenation in Chronic Maternal Hypoxia; What’s Critical?

Abstract

For the study in an animal model of the consequences of chronic maternal hypoxia on several physiological variables (e.g., fetal ECG variability, fetal breathing patterns), as potential clinical indicators for insufficient oxygen supply to the fetus, the continuous availability of a reliable signal on fetal oxygenation is necessary. This signal is needed as a feedback for the control of maternal inspiratory oxygen fraction (F¹O₂) in the model. Theoretically, fetal arterial oxygen saturation is the indicator of choice for the observation of oxygen availability, assuming hemoglobin concentration is normal as well as constant. The development [1] of pulse oximetry as a non-invasive optical technique seemed promising for the application in fetal studies [2], especially in chronically instrumentated fetal lambs. To evaluate the possibilities of this technique, we tested pulse oximetry transducers, both in transmission and reflection mode, against blood gas analysis before, during and after periods of maternal hypoxia in sheep. From the results of the blood gas measurements we tried to find objective criteria to determine the onset of fetal endanger, induced by maternal hypoxia.