Validation of Transabdominal Fetal Pulse Oximetry in Hypoxic Fetal Lamb Models

项目摘要 尽管剖腹产的成本很高，而且有明显的证据表明剖腹产会带来健康风险， 在美国，不必要地大量婴儿通过剖腹产分娩。剖腹产的高比率 相对于全球公认的标准，在美国，部分原因是胎儿窘迫的假阳性率很高， 与目前已有半个世纪历史的产时胎儿监测技术有关。长期构想 该项目的目的是通过开发一种改进的、更具体的技术来缓解这一问题， 产时胎儿健康监测。 具体来说，我们已经开发了这项技术，并建立了一个设备原型，用于非侵入性，经腹 测量胎儿动脉血氧饱和度（FSpO2）。该装置的工作原理是在 腹部区域在两个特定的近红外波长，其次是感测弱回散射光 透射反射随后处理感测到的信号以去除各种噪声， 包括不想要的母亲贡献，从测量结果中推断光强度的变化 这是由胎儿动脉搏动引起的该设备原型成功地验证了几个 初步测试，包括模拟，人体受试者的光电体积描记（PPG）采集， 厚光学体模模仿孕妇腹部区域的光学特性，PPG检测 以及通过仿真母体组织分离仿真胎儿信号，以及在 缺氧胎羊模型。 为了进一步发展这项技术，我们的目标是研究设备在测量FSpO2方面的准确性和可靠性 在缺氧胎羊模型中（n=18）。我们的动物研究方案，已经证明是有效的， 初步工作包括子宫切开术，为羊胎儿插管，以监测胎儿血流动力学， 抽取胎儿血液样本，并在母体主动脉中放置可充气导管， 调节母羊子宫的血液供应，并诱导可控的胎儿缺氧。这项研究将使我们能够 通过动脉血气（ABG）测试收集金标准胎儿动脉血氧饱和度（FSaO2）数据， 在一些缺氧的情况下，并将它们与我们的设备的并发测量进行比较。 这项研究分为两个互补的小组，这取决于子宫周围是否关闭。 胎儿颈部（n=9）或胎儿完全返回子宫（n=9），然后关闭母羊的腹部筋膜， 使我们能够隔离不同组织层的影响，并描述该技术的操作范围 和局限性。该项目将为释放潜在的临床影响提供基础， 技术在路上。

Project Summary Despite significant cost and clear evidence of health risks associated with Cesarean deliveries (C-sections), an unnecessarily large number of infants are delivered via C-sections in the US. The high rate of C-sections in the nation, relative to globally accepted norms, is in part attributed to the high false positive rate of fetal distress, associated with the current half-a-century-old intrapartum fetal monitoring technology. The long-term vision of this project is to alleviate this problem, by developing an improved and more specific technology for intrapartum fetal health monitoring. Specifically, we have developed the technology and built a device prototype for non-invasive, transabdominal measurement of fetal arterial blood oxygen saturation (FSpO2). The device works by shining light in the abdominal area at two specific near infrared wavelengths, followed by sensing the weak back scattered light reflections transcutaneously. The sensed signals are subsequently processed to remove various noises, including the unwanted maternal contributions, from the measurements to infer variations in light intensity that are strictly due to pulsation of fetal arteries. The device prototype is successfully validated in several preliminary tests, including simulations, photo-plethysmography (PPG) acquisition in human subjects through a thick optical phantom mimicking optical properties of a pregnant woman's abdominal area, PPG detection and separation of emulated fetal signal through an emulated maternal tissue, and in-vivo validation in a hypoxic fetal lamb model. To further advance the technology, we aim to investigate device's accuracy and reliability in measuring FSpO2 in hypoxic fetal lamb models (n=18). Our animal study protocol, already demonstrated to be effective in our preliminary work, includes hysterotomy to cannulate lamb fetus for fetal hemodynamic monitoring and drawing fetal blood samples, and placement of an inflatable catheter in the maternal aorta through which, we regulate the ewe's blood supply to the uterus, and induce controllable fetal hypoxia. The study will enable us to collect gold standard fetal arterial blood oxygen saturation (FSaO2) data via arterial blood gas (ABG) tests, under a number of hypoxia scenarios, and to compare them against our device's concurrent measurements. The study is organized into two complementary groups, depending on whether the uterus is closed around the fetal neck (n=9) or the fetus is fully returned to the uterus (n=9) before closing ewe's abdominal fascia, which enables us to isolate the impact of different tissue layers, and to characterize the technology's operating range and limitations. The project will provide the foundation for unleashing the potential clinical impact of the technology down the road.