The search for non-invasive methods for determining fetal well-being in utero continues. Despite the introduction of electronic fetal heart rate monitoring, the overall rate of fetal hypoxia at birth has not decreased. The observed increase in the cesarean delivery rate since the introduction of continuous fetal monitoring is concerning. The goal of this project is to examine the accuracy of near infrared transabdominal fetal oximetry in determining fetal blood oxygenation, an important reflection of fetal well-being. The hope is to make a positive clinical impact on both improved neonatal outcome and reduction of the cesarean section rate. It is our proposal here to extend the penetration depth of safe and affordable NIR technology from the few cm for which significant results have been obtained in muscle, brain and breast to the depth (within the maternal abdomen) at which the fetal head is located for near term fetus. Obtaining this goal will enable us to quantify and image fetal brainoxygenation and blood volume for identifying fetuses at risk. A successful """"""""Runman"""""""" type of dual wavelength spectrophotometer (tungsten lights, silicon diodes, with dichroic filters) has been improved to use a 10 cm source/detector separation to give blood volume and oxygenation trend signals from 30 pregnant mothers. These data have shown correlations of blood volume and oxygenation increase when the heart rate monitor has shown spontaneous increases of heart rate or when the startle reflex has been induced by a buzzer to activate the fetus. Three improvements of the device would provide localized signals from the fetal head; one, the use of three """"""""Runman"""""""" type of sensors; two, a series of concentric circles of sources and detectors surrounding the abdomen; and three, multiple source/detector combinations (21 detectors and 9 dual wavelength sources) with an appropriate algorithm (initially back projection to image the head of the baby in utero) is proposed. The fetal head can further be distinguished from maternal signals by using the higher heart rate of the fetus. Here, phase locked loop technology will be used to track the fetal arterial pulse and to separate the fetal and maternal signals. The Phase I feasibility trials will be followed by Phase ll construction and test of the most appropriate instrument for in utero fetal oxygen monitoring.
In utero brain monitoring will open a new market for """"""""preventive"""""""" medical devices that monitor the oxygen status of the fetal brain, immediately, noninvasively, safely and affordably. Obtaining additional information which will be used to determine whether less aggressive or more aggressive clinical intervention is required in order to prevent cerebral palsy and other brain damage occurrences will result in healthier children. The market can be expected to include both in-hospital and where necessary at-home monitoring and thus, may be expected to be a large fraction of the pregnant population.
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| Ramanujam, N; Vishnoi, G; Hielscher, A et al. (2000) Photon migration through fetal head in utero using continuous wave, near infrared spectroscopy: clinical and experimental model studies. J Biomed Opt 5:173-84 |
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