This project addresses the critical need for real time quantification of fetal hypoxia, a condition of concern during all births that can lead to brain damage or death. Currently, no such direct monitor of hypoxia exists, yet each year half of births are monitored with some indirect indicator of hypoxia. The American College of Obstetricians and Gynecologists has recommended that arterial acidity be measured in newborns with persistently depressed Apgar scores to determine if hypoxia is a proximate cause. During Phase I, TTI has developed a membrane covered polarographic oxygen sensor which also incorporates a thermistor to measure the local blood perfusion rate to address this clinical need. This scalp- contacting sensor uses protocols adapted from Thermal Technologies' Enhanced Thermal Diffusion Probe to measure oxygen tension (1 mmHg), perfusion (10%) and temperature (0.0035 degrees C). The Bilayer Membrane eliminates pressure sensitivity of the polarographic oxygen sensor as well as operator-specific calibration variability. This membrane consists of a tissue contacting silicone gas permeable membrane bonded to a saline- saturated hydrogel to provide electrical continuity between the cathode and anode. During Phase II, the sensor performance will be optimized for stability and temporal response. The on probe current to voltage amplification of the polarographic signals will be fabricated using hybrid electronic packaging to reduce overall probe size. A retractable-staple attachment mechanism will be designed and tested. Following this, Phase II work will be devoted to both the evaluation of the integrated system as well as verification of its clinical relevance. This will be done through measurements on the fetuses of pregnant ewes in ongoing experimentation with our clinical collaborators.
