Evaluation of fetal oxygen saturation (SpO_2) during labor and effects of maternal oxygen administration on fetal SpO_2

本研究的目的是研制一种新型反射式脉搏血氧饱和度测定仪，在分娩过程中连续、无创地测量胎儿SpO_2，评价胎心率(FHR)与胎儿SpO_2的相关性，并评价母亲吸氧对胎儿SpO_2的影响。在知情同意的情况下，宫颈扩张超过5 cm，宫袋破裂的情况下，反射式探头适用于胎儿前额。同时监测胎儿SpO2和FHR。结果：1)研制了鞋角型反射式探头，LED与传感器之间的距离为10 mm。(2)胎儿出生前SpO_2与脐动脉血SaO_2有良好的相关性(y=0.97_X-7.28)。(3)胎儿宫口扩张5~7 cm时SpO_2正负13%。SpO_2在扩张8-9 cm时为60&lt；+--11%。第二阶段的SpO_2为56&lt；正负-11%。出生前SpO_2为48&lt；+-13%，明显低于其他各期。4)早期减速不会降低胎儿SpO_2。2)晚期减速和重度变速减速显著降低胎儿SpO_2。2)母血供氧降低胎儿基础SpO_2(50%)可使胎儿SpO_2显著升高。结论：1)临产时胎儿SpO_2维持在55%以上，临产前降低到50%以下。(2)晚期减速和重度可变减速降低胎儿血氧饱和度(SpO_2)。(2)母体用药可有效提高低氧胎儿的血氧饱和度(SpO_2)。

The purposes of study were to develop a new reflectance pulse oximetry probe which enables us to measure fetal SpO_2 during labor continuously and non-invasively and to evaluate correlation between fetal heart rate (FHR) and fetal SpO_2. And effect of maternal oxygen administration to fetal SpO_2 was estimated.Patients and methods : 120 patients from 30 to 41 weeks were measured. The reflectance probe was adapted to the fetal forehead, on condition that uterine cervix was dilated more than 5cm with rupture of the bag with informed consent. Fetal SpO_2 and FHR was simultaneously monitored. Oxygen was administrated by a rate 5/min by nasal connula after obtained informed consent.Results : 1) The shoe-horn typed reflectance probe, 10mm between LED and sensor, was developed. 2) Good correlation between fetal SpO_2 just before birth and umbilical arterial blood SaO_2 was confirmed (y=0.97_X-7.28). 3) Fetal SpO_2 at cervical os 5-7cm dilated was 56<plus-minus>13%. SpO_2 at 8-9cm dilated was 60<plus-minus>11%. SpO_2 in second phase was 56<plus-minus>11%. SpO_2 just before birth was 48<plus-minus>13% and significantly lower than other stages. 4) Early deceleration did not decrease fetal SpO_2.5) Late deceleration and severe variable deceleration significantly decreased fetal SpO_2.6) Maternal oxygen administration to lower fetal baseline SpO_2 (50%) led to significant increase of fetal SpO2.Conclusion : 1) Fetal SpO_2 during labor remains above 55% and decreased below 50% just before birth. 2) Late deceleration and severe variable deceleration decrease fetal SpO_2.3) Maternal oygen administration is effective for hypoxic fetuses to increase SpO_2. Reflectance pulse oximetry may have potential to be a good tool in monitoring fetal wellbeing during labor.