PHOTOACOUSTICS: Optoacoustic method aims to improve fetal monitoring during delivery

Fetal heart rate monitoring during labor and delivery was introduced into practice in the 1970s without clinical trials. The method continues to be the only form of fetal monitoring used during late-stage labor—despite its inefficiency and continuing controversy. With an 89%+ false-positive prediction of fetal distress and prone to inconsistent interpretations, fetal heart rate monitoring has not produced better outcomes.

Now, Noninvasix (Galveston, TX) offers a novel solution based on photoacoustics. Unlike traditional fetal heart rate systems, which use changes in basal heart rate to indirectly assess fetal asphyxia, the new technology monitors cerebral venous oxygenation in the superior sagittal sinus to quickly and directly detect the amount of oxygen a baby is receiving.

The superior sagittal sinus (SSS) is a large central cerebral vein located immediately beneath the top of the human skull in the midline. Using a transvaginal, optoacoustic probe, short laser pulses directed into the SSS generate optoacoustic waves, which are sent to an electronic monitoring system for signal amplification, acquisition, and recording with a PC. Because the generated ultrasound signal returns in a straight line from the superior sagittal sinus, the actual saturation of hemoglobin in the superior sagittal sinus can be accurately determined. The patented technology provides accurate measurement of oxygenation due to high (optical) contrast and high (ultrasound) resolution that permits direct probing of blood vessels.

Moreover, because cerebral venous desaturation provides direct evidence that cerebraloxygen availability is insufficient to satisfy cerebral oxygen requirements, studies suggest that decreasing levels of SSS (SO₂) can provide an early warning of neonatal cerebral hypoxia.